All creatures have one quarter concealment at 15 metres (-1 to hit), one half concealment at 30 metres (-2 to hit), three quarters concealment at 45 metres (-3 to hit), and nine-tenths concealment at 60 metres (-4 to hit). Beyond 60 metres creatures have total concealment (-6 to hit), and opponents cannot use sight to locate the creature. 

Murkier water allows less sighting distance, and creatures become completely concealed more quickly. The maximum sighting distance in murky water is 30 metres. 

At half the listed distance creatures have one half concealment, at the listed distance creatures have nine tenths concealment, and they have total concealment beyond the listed distance. For example, if murky water allows vision to 12 metres, creatures have one half concealment at 6 metres, nine tenths concealment at 12 metres, and total concealment beyond 12 metres. Water can be so murky that it allows vision to 1.5mtrs or none at all. Aquatic creatures can see twice as far through the water as other creatures (but twice nothing is still nothing).

All of this points to the trouble a clothed and armoured man has in water. Clothes become waterlogged rapidly, and their weight affects both buoyancy and DEX, with a minimum DEX loss of 2 points. Shoes absorb an additional 1 DEX point; boots, 2 DEX points. All types of armour except chain mail have 30% added to their weight; all types of armour except plate mail add 1 to the wearer's DEX loss, and plate mail doubles its DEX loss.

If two men grapple in the water (two combatants, or a drowning victim clutching in panic at his rescuer), all of their DEX are used in combat and cannot be used for buoyancy. (The same is true of a man who is entangled.) Men in this condition rise or sink according to their combined buoyancy, with -2 buoyancy added to their total to account for the effects of mutual awkwardness in water.

Normal exertion
Time spent active in water is always costly in stamina for a landsman. Whenever a character spends a significant portion of any given hour in water treat as though he had been carrying 28kgs of weight for a full hour, and work out his fatigue according to his CON. The exercise rate should be read as one level higher than the same exercise on land. This does not include fatigue from anything being carried, pushed, or towed in water for a significant amount of time. Determine this separately, again at a rate one level higher than on land.

Drowning
Drowning is the greatest danger a character faces in the water. Aquatic enemies may or may not be present in any given situation, but wherever there is water, there is the danger of drowning. For game purposes, drowning is a process of fatigue and CON loss. In the round a character is declared to be drowning, he loses 1 HP, and then continues to lose 1 HP every round thereafter. When he has lost all HPs, he is stunned. In the following round, CON loss begins at the rate of 1 point per round. When all CON points are gone, the character is dead. Once drowning has begun, the process continues until it is corrected by direct action, or until the character dies. Drowning may result from several things. Whenever a character underwater uses up all his breath time, he is declared to be drowning. Swim rate is reduced to 1/3 MR (plus buoyancy ascent rate), and the character immediately makes a WIS test to see if he panics. If he succeeds he retains his self-control and can continue to help himself (by releasing his weight belt if he hasn't already done so, for example). If he fails, he panics and can no longer help himself. A character who is stunned in or under the water is also declared to be drowning. He cannot recover from being stunned or panicked until after the drowning process is stopped (presuming he's rescued). Panic may result from anything that would cause panic on land. All panicked victims begin to drown.

1) Moving from one base to another, 

2) Conducting an anti-piracy patrol and there is a 60% chance of stopping the player's vessel to check the cargo and passengers,

3) Seeking to engage an enemy fleet or 

The epipelagic (euphotic) zone - also called the sunlit zone, receives enough sunlight to support photosynthesis. The temperatures in this zone range anywhere from 40 to −3 °C. The epipelagic zone is the one closest to the surface and is the best lit. It extends to 200 metres and contains both phytoplankton and zooplankton that can support larger organisms like marine mammals and some types of fish. This is the top layer, nearest the surface. Here there is enough light penetrating the water to support photosynthesis. More than ninety percent of all marine life lives in the sunlit zone. The sunlit zone goes down about 600 metres. Most fish and other sentient races live in this zone.

The mesopelagic (disphotic) zone - where only small amounts of light penetrate, lies below the epipelagic zone. This zone is often referred to at the Twilight Zone due to its scarce amount of light. Temperatures in the mesopelagic zone range from 5 to 4 °C. The pressure is higher here, it can be up to 1,470 pounds per square inch (10,100,000 Pa) and increases with depth. Only a small amount of light can penetrate the water at this depth. As the water becomes deeper, the pressure also increases. Plants do not grow here. Only animals that have adapted to low light survive. The nommo and the Cerulean nixie call this zone home. This gloomy part of the ocean begins at about 600 metres under the water and extends to the darkest part, which begins about 3000 metres down. Bioluminescent creatures abound in this zone.

The bathypelagic (aphotic) zone - 90% of the ocean lies here in which no light penetrates. This is also called the midnight zone. Water pressure is very intense and the temperatures are near freezing range 0 to 6 °C. It is oppressively dark, the water pressure is extreme, and the temperature is near freezing. Living creatures found here live close to cracks in the planet's crust. These cracks give off mineral-rich materials that nourish bacteria, which form the bottom of the food chain here, much like plankton does in the waters above. Deep drow, the aquatic equivalent of the surface dark elves, claim this realm as their own.

Past 200 metres, not enough light penetrates the water to support life, and no plant life exists. There are creatures however, which thrive around hydrothermal vents, or geysers located on the ocean floor that expel super heated water that is rich in minerals. These organisms feed off of chemosynthetic bacteria, which use the super heated water and chemicals from the hydrothermal vents to create energy in place of photosynthesis. The existence of these bacteria allow creatures like squids, hatchet fish, octopuses, tube worms, giant clams, spider crabs and other organisms to survive. Due to the total darkness in the zones past the epipelagic zone, many organisms that survive in the deep oceans do not have eyes, and other organisms make their own light with bioluminescence. Often the light is blue green in colour, because many marine organisms are sensitive to blue light. Two chemicals, luciferin and luciferase that react with one another to create a soft glow. The process by which bioluminescence is created is very similar to what happens when a glow stick is broken. Deep-sea organisms use bioluminescence for everything from luring prey to navigation. Animals such as fishes, whales, and sharks are found in the oceanic zone.

The ocean floor is not as flat and sandy as their more-familiar beaches, nor quite so predictable. In addition to the aquatic mountains, valleys, deserts, and plains, there are features that are foreign to those that live solely on land.
As the land descends beneath the sea, there are drastic changes in the planet's geology. This transitional area, known as the continental margin, includes both the continental shelf and the continental slope. As dry-land fades from sight, the heavy and thick continental granite gives way to a thinner layer of basalt. The continental shelf normally contains water that is only a couple of hundred metres deep. The neritic zone is located here. The width of the continental shelf varies greatly depending on location. At the edge of the continental shelf, the ocean floor begins a steep descent known as the continental slope. This area is often pervaded by fathomless submarine canyons. The slope levels out at the ocean basin, which also has some interesting features. Perhaps the most unusual are the abyssal plains which are large, flat areas on the ocean floor covered with a thick layer of sediment and decomposing organic ooze. Large, undersea volcanoes called seamounts occasionally rise from these depths. Sometimes the peaks of these giant underwater volcanoes reach to the surface to form volcanic islands. Ocean trenches are found along the edge of ocean basins. These trenches contain the deepest parts of the ocean, and therefore, the deepest parts of the world. They can go down several kilometres, and are known to harbor the most terrible abominations that one could imagine.

In contrast to terrestrial habitats, marine habitats are shifting and ephemeral. Swimming organisms find areas by the edge of a continental shelf a good habitat, but only while upwellings bring nutrient rich water to the surface. Shellfish find habitat on sandy beaches, but storms, tides and currents mean their habitat continually reinvents itself. The presence of seawater is common to all marine habitats. Beyond that many other things determine whether a marine area makes a good habitat and the type of habitat it makes. For example:
Temperature – is affected by geographical latitude, ocean currents, weather, the discharge of rivers, and by the presence of hydrothermal vents or cold seeps.
Sunlight – photosynthetic processes depend on how deep and turbid the water is.
Nutrients – are transported by ocean currents to different marine habitats from land runoff, or by upwellings from the deep sea, or they sink though the sea as marine snow.
Salinity – varies, particularly in estuaries or near river deltas, or by hydrothermal vents.
Dissolved Gases – oxygen levels in particular, can be increased by wave actions and decreased during algal blooms.
Acidity – this is partly to do with dissolved gases above, since the acidity of the ocean is largely controlled by how much carbon dioxide is in the water.
Turbulence – ocean waves, fast currents and the agitation of water affect the nature of habitats.
Cover – the availability of cover such as the adjacency of the sea bottom, or the presence of floating objects
the occupying organisms themselves since organisms modify their habitats by the act of occupying them, and some, like corals, kelp, mangroves and seagrasses, create further habitats for other organisms.

The pelagic part of the aphotic zone can be further divided into vertical regions according to temperature. The mesopelagic is the uppermost region. Its lowermost boundary is at a thermocline of 12 °C, which, in the tropics generally lies at 700–1000 metres. Next is the bathypelagic lying between 10 and 4 °C, typically between 700–1000 metres and 2,000–4,000 metres. Lying along the top of the abyssal plain is the abyssopelagic, whose lower boundary lies at about 6,000 metres. The last zone includes the deep oceanic trench, and is known as the hadalpelagic. This lies between 6,000–11,000 metres and is the deepest oceanic zone. The benthic zones are aphotic and correspond to the three deepest zones of the deep-sea. The bathyal zone covers the continental slope down to about 4000 metres. The abyssal zone covers the abyssal plains between 4000 and 6000 m. Lastly, the hadal zone corresponds to the hadalpelagic zone, which is found in oceanic trenches.
The pelagic zone can be further subdivided into two subregions: the neritic zone and the oceanic zone. The neritic zone encompasses the water mass directly above the continental shelves whereas the oceanic zone includes all the completely open water.
In contrast, the littoral zone covers the region between low and high tide and represents the transitional area between marine and terrestrial conditions. It is also known as the intertidal zone because it is the area where tide level affects the conditions of the region.

As a result, coastal marine life is the most abundant in the world. It is found in tidal pools, fjords and estuaries, near sandy shores and rocky coastlines, around coral reefs and on or above the continental shelf. Coastal fish include small forage fish as well as the larger predator fish that feed on them. Forage fish thrive in inshore waters where high productivity results from upwelling and shoreline run off of nutrients. Some are partial residents that spawn in streams, estuaries and bays, but most complete their life cycle in the zone. There can also be a mutualism between species that occupy adjacent marine habitats. For example, fringing reefs just below low tide level have a mutually beneficial relationship with mangrove forests at high tide level and sea grass meadows in between: the reefs protect the mangroves and seagrass from strong currents and waves that would damage them or erode the sediments in which they are rooted, while the mangroves and seagrass protect the coral from large influxes of silt, fresh water and pollutants. This additional level of variety in the environment is beneficial to many types of coral reef animals, which for example may feed in the sea grass and use the reefs for protection or breeding. Coastal habitats are the most visible marine habitats, but they are not the only important marine habitats. Coastlines run for 380,000 kilometres, and the total volume of the ocean is 1,370 million cu km. This means that for each metre of coast, there is 3.6 cu km of ocean space available somewhere for marine habitats. Waves and currents shape the intertidal shoreline, eroding the softer rocks and transporting and grading loose particles into shingles, sand or mud.

Intertidal zones, those areas close to shore, are constantly being exposed and covered by the ocean's tides. A huge array of life lives within this zone. Shore habitats range from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of bioerosion.

Sandy shores, also called beaches, are coastal shorelines where sand accumulates. Waves and currents shift the sand, continually building and eroding the shoreline. Longshore currents flow parallel to the beaches, making waves break obliquely on the sand. These currents transport large amounts of sand along coasts, forming spits, barrier islands and tombolos. Longshore currents also commonly create offshore bars, which give beaches some stability by reducing erosion. Sandy shores are full of life, The grains of sand host diatoms, bacteria and other microscopic creatures. Some fish and turtles return to certain beaches and spawn eggs in the sand. Birds habitat beaches, like gulls, loons, sandpipers, terns and pelicans. Aquatic mammals, such sea lions, recuperate on them. Clams, periwinkles, crabs, shrimp, starfish and sea urchins are found on most beaches. Sand is a sediment made from small grains or particles with diametres between about 60 µm and 2 mm. Mud is a sediment made from particles finer than sand. This small particle size means that mud particles tend to stick together, whereas sand particles do not. Mud is not easily shifted by waves and currents, and when it dries out, cakes into a solid. By contrast, sand is easily shifted by waves and currents, and when sand dries out it can be blown in the wind, accumulating into shifting sand dunes. Beyond the high tide mark, if the beach is low-lying, the wind can form rolling hills of sand dunes. Small dunes shift and reshape under the influence of the wind while larger dunes stabilise the sand with vegetation. Ocean processes grade loose sediments to particle sizes other than sand, such as gravel or cobbles. Waves breaking on a beach can leave a berm, which is a raised ridge of coarser pebbles or sand, at the high tide mark. Shingle beaches are made of particles larger than sand, such as cobbles, or small stones. These beaches make poor habitats. Little life survives because the stones are churned and pounded together by waves and currents.

Tidepools on rocky shores make turbulent habitats for many forms of marine life. The relative solidity of rocky shores seems to give them a permanence compared to the shifting nature of sandy shores. This apparent stability is not real over even quite short geological time scales, but it is real enough over the short life of an organism. In contrast to sandy shores, plants and animals can anchor themselves to the rocks. Competition can develop for the rocky spaces. For example, barnacles can compete successfully on open intertidal rock faces to the point where the rock surface is covered with them. Barnacles resist desiccation and grip well to exposed rock faces. However, in the crevices of the same rocks, the inhabitants are different. Here mussels can be the successful species, secured to the rock with their byssal threads. Rocky and sandy coasts are vulnerable because humans find them attractive and want to live near them. An increasing proportion of the humans live by the coast, putting pressure on coastal habitats.

Mudflats are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays, bayous, lagoons, and estuaries. Mudflats may be viewed geologically as exposed layers of bay mud, resulting from deposition of estuarine silts, clays and marine animal detritus. Most of the sediment within a mudflat is within the intertidal zone, and thus the flat is submerged and exposed approximately twice daily. Mudflats are typically important regions for wildlife, supporting a large population, although levels of biodiversity are not particularly high. They are of particular importance to migratory birds. In the United Kingdom mudflats have been classified as a Biodiversity Action Plan priority habitat.

Mangrove swamps and salt marshes form important coastal habitats in tropical and temperate areas respectively.
Mangroves are species of shrubs and medium size trees that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. The saline conditions tolerated by various species range from brackish water, through pure seawater (30 to 40 ppt), to water concentrated by evaporation to over twice the salinity of ocean seawater (up to 90 ppt). There are many mangrove species, not all closely related. The term "mangrove" is used generally to cover all of these species, and it can be used narrowly to cover just mangrove trees of the genus Rhizophora. Mangroves form a distinct characteristic saline woodland or shrubland habitat, called a mangrove swamp or mangrove forest'. Mangrove swamps are found in depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. Mangroves dominate three quarters of tropical coastlines.

The morphological structure of a kelp thallus is defined by three basic structural units:
The holdfast is a root-like mass that anchors the thallus to the sea floor, though unlike true roots it is not responsible for absorbing and delivering nutrients to the rest of the thallus;
The stipe is analogous to a plant stalk, extending vertically from the holdfast and providing a support framework for other morphological features;
The fronds are leaf- or blade-like attachments extending from the stipe, sometimes along its full length, and are the sites of nutrient uptake and photosynthetic activity.
In addition, many kelp species have pneumatocysts, or gas-filled bladders, usually located at the base of fronds near the stipe. These structures provide the necessary buoyancy for kelp to maintain an upright position in the water column.

In the open ocean, sunlit surface epipelagic waters get enough light for photosynthesis, but there are often not enough nutrients. As a result, large areas contain little life apart from migrating animals. The surface waters are sunlit. The waters down to about 200 metres are said to be in the epipelagic zone. Enough sunlight enters the epipelagic zone to allow photosynthesis by phytoplankton. The epipelagic zone is usually low in nutrients. This partially because the organic debris produced in the zone, such as excrement and dead animals, sink to the depths and are lost to the upper zone. Photosynthesis can happen only if both sunlight and nutrients are present. In some places, like at the edge of continental shelves, nutrients can upwell from the ocean depth, or land runoff can be distributed by storms and ocean currents. In these areas, given that both sunlight and nutrients are now present, phytoplankton can rapidly establish itself, multiplying so fast that the water turns green from the chlorophyll, resulting in an algal bloom. These nutrient rich surface waters are among the most biologically productive in the world, supporting billions of tonnes of biomass.

"Phytoplankton are eaten by zooplankton - small animals which, like phytoplankton, drift in the ocean currents. The most abundant zooplankton species are copepods and krill: tiny crustaceans that are the most numerous animals on Earth. Other types of zooplankton include jelly fish and the larvae of fish, marine worms, starfish, and other marine organisms". In turn, the zooplankton are eaten by filter feeding animals, including some seabirds, small forage fish like herrings and sardines, whale sharks, manta rays, and the largest animal in the world, the blue whale. Yet again, moving up the foodchain, the small forage fish are in turn eaten by larger predators, such as tuna, marlin, sharks, large squid, seabirds, dolphins, and toothed whales. The deep sea starts at the aphotic zone, the point where sunlight loses most of its energy in the water. Many life forms that live at these depths have the ability to create their own light a unique evolution known as bio-luminescence. In the deep ocean, the waters extend far below the epipelagic zone, and support very different types of pelagic life forms adapted to living in these deeper zones.[56]
Much of the aphotic zone's energy is supplied by the open ocean in the form of detritus. In deep water, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. Its origin lies in activities within the productive photic zone. Marine snow includes dead or dying plankton, protists (diatoms), fecal matter, sand, soot and other inorganic dust. The "snowflakes" grow over time and may reach several centimetres in diametre, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres of their journey, that is, within the epipelagic zone. In this way marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems: As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. Some deep-sea pelagic groups, such as the lanternfish, ridgehead, marine hatchetfish, and lightfish families are sometimes termed pseudoceanic because, rather than having an even distribution in open water, they occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes. The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures.

The fish in the different pelagic and deep water benthic zones are physically structured, and behave in ways, that differ markedly from each other. Groups of coexisting species within each zone all seem to operate in similar ways, such as the small mesopelagic vertically migrating plankton-feeders, the bathypelagic anglerfishes, and the deep water benthic rattails. Ray finned species, with spiny fins, are rare among deep sea fishes, which suggests that deep sea fish are ancient and so well adapted to their environment that invasions by more modern fishes have been unsuccessful. The few ray fins that do exist are mainly in the Beryciformes and Lampriformes, which are also ancient forms. Most deep sea pelagic fishes belong to their own orders, suggesting a long evolution in deep sea environments. In contrast, deep water benthic species, are in orders that include many related shallow water fishes.
The umbrella mouth gulper is a deep sea eel with an enormous loosely hinged mouth. It can open its mouth wide enough to swallow a fish much larger than itself, and then expand its stomach to accommodate its catch.

Beaches - consist of a sandy or rocky shore, usually with very sparse vegetation, if any. The beach is home to a variety of sea creatures who take advantage of easy access to land and water.

Boulder - Boulders come in many shapes and sizes, but are generally D6 metres tall and are quite slippery, especially if they rest below the high-tide line. A climb skill roll is required to navigate such a rock successfully while walking upon them. If the boulder is underwater, the character can swim over it without penalty.

Coral, dead - Coral reefs are usually encountered in warm waters and are made up of thousands of different varieties of living coral. They are home to countless sea creatures and are very rich in biodiversity. Coral reefs generally occur in water that is 4D6 metres deep, and can grow to a height of up to 6D6 metres tall, so long as this remains at least 2 metres below the water’s surface. Although rare, deepwater coral reefs also exist as far down as 100 metres, and are usually lit with spectacular bioluminescence. A coral reef itself, regardless of depth, can be anywhere from 6 metres to several kilometres in diametre. It also occurs in narrow strips that can be only a few metres wide, but several kilometres long. Living coral reefs are built upon dead coral (calcium-rich skeletons of living coral). It is usually pale and worn, often appearing as irregularly shaped stone. Navigating areas of dense dead coral can be tricky.

Coral, living - Entering the area of a living coral reef can be extremely dangerous for any creature of Small size or greater. It is inhabited by all manner of living spines, branches, stingers, and tentacles. A creature entering a square containing living coral much make an Acrobatics skill roll, or get scratched, stung, or stabbed by the coral. Treat this effect as a slashing melee attack with a +4 attack bonus that deals 1 point of damage.

Coral, surfacing - Surfacing coral is mostly dead coral that reaches up beyond two metres below the water’s surface. It is periodically exposed to the air from the action of waves and tide. Due to its irregular formation and shallow depth, it is impossible to swim through an area of surfacing coral.

Coral Wall - Dead coral can be hewn into bricks and structures much like stone. When a coral wall divides two chambers, it is usually at least 3 metres thick in order to bear the weight of the coral above. It requires a climb check to climb a wall made of dead coral.

Driftwood - Wood of all varieties washes up along the beach regularly. It has a characteristically worn appearance including smooth and twisted shapes and sun-bleached pallor. It can form huge piles that act as natural barriers. Moving into these barriers both above and below the water costs one square. It also provides low cover.

Dune - Dunes are steep piles of loose sand that are often formed by water currents or wind. Dunes are usually around 4D6 metres long, and D4 metres tall. Creatures that run or charge down a dune must first succeed on an Acrobatics skill roll or slide downwards. If the check fails by more than 4, the character also falls prone at the end of the slide. Underwater sand dunes are called sand bars, and work the same way if the character is moving along the sea floor. However, a character can also swim over these features without movement penalty.

Flowing Water - Large, placid rivers move at only a few kilometres per hour, so they function as still water for most purposes. But some rivers and streams are swifter; anything floating in them moves downstream at a MR of 10 to 40. The fastest rapids send swimmers bobbing downstream at 60 to 90 MR. Fast rivers are always at least rough water, and whitewater rapids are stormy water. If a character is in moving water, move him downstream the indicated distance at the end of his turn. Characters swept away by a river moving 60 or faster must make swim checks every round to avoid going under. Escaping the rapids by reaching the bank requires three swim checks in a row. Characters arrested by a rock, limb, or snag can’t escape under their own power unless they strike out into the water and attempt to swim their way clear. Other characters can rescue them as if they were trapped in quicksand.

Gravel - Gravel bottoms are common in colder ocean waters, and are often inundated with many varieties of seaweed. While easier to manoeuvre through than muck, gravel bottoms are slicker than a clear sandy bottom. Running and charging are impossible in this terrain feature, as there is no good way to get footing.

Hydrothermal Vent - Also called “hot springs” if they occur in shallow water, a hydrothermal vent is a fissure in the planet's surface from which geothermal-heated water issues. Hydrothermal vents are often found near volcanic activity. The temperature of these areas can range from pleasantly warm to scalding hot.

Iceberg - An iceberg is a gigantic block or mass of ice that has broken off from a glacier or ice shelf. This iceberg then floats in the world's oceans and moves via wind and ocean currents. Icebergs are famous for their size and their ability to hide it under water. Typically, only one-tenth of an iceberg's volume is visible above the water's surface, while most of its mass is below. In general, the total size of the average iceberg is D6 × 25 metres above sea level, with another 3D10 × 25 metres below sea level. They are typically D6 × 30 metres across. Icebergs can be several kilometres across and several hundred metres tall, however. These super-sized icebergs often break up into smaller icebergs when they reach warm waters. Despite their size, icebergs move an average speed of 3 kilometres per day.

Kelp forests - can be seen along much of the coasts of the Cerulean Seas. Kelp is large brownish-green seaweed that lives in cool, shallow waters close to the shore. It grows in thick groupings much like a forest on land. These submerged towers of kelp provide sustenance and shelter for thousands of fish, invertebrates, and marine mammal species. In fact, kelp forests harbour a greater assortment of plants and animals than nearly any other aquatic
community. Many creatures use the thick blades of kelp as a safe shelter from predators for their young or from stormy weather. Any creature in a square of kelp forest has concealment. A creature more than 1 metre away in kelp forest has total concealment. The top of a kelp forest is generally 3D10 metres from the surface of the water and can grow to a height of D6 metres from the sea floor. Some varieties of kelp can grow hundreds of metres long. Kelp forests can be anywhere from a few hundred metres to several kilometres in size.

Muck - Abyssal floors, estuaries, and tidewaters are commonly covered in muck up to three metres deep. Running and charging are impossible.

Nonflowing Water - Lakes and oceans simply require a swim check to move through. Characters need a way to breathe if they’re underwater; failing that, they risk drowning. When underwater, characters can move in any direction as if they were flying with perfect manoeuvrability.

Pass - Passes are meandering cracks and spaces between the coral, usually with a sandy bottom that is also devoid of coral. A pass is typically 2 metres wide. They range from 3 to 30 metres long, and often branch out to several other passes forming a huge labyrinth.

Pit - Much like a pass, a pit is a gap in the coral the leads to a sandy bottom. It is usually one metre in diametre, and can go down D10 metres. This can be an unforeseen obstacle while walking along the top of the coral. A perception roll is required to notice a pit. Failure to notice a pit means a walking character is now swimming, and subject to the rules of buoyancy. If the pit occurs in an area of living coral, the unwary character will also be subject to being scraped by the coral as if entering the square for the first time.

Rock Reef - A rock reef is a quantity of underwater stone which is usually heavily overrun with anemones, barnacles, shellfish, and other small underwater creatures. A rock reef can function as a wall or steep slope underwater,
although swimmers can simply go over or around them. Whenever a ship travels through shallow water, either reefs or near islands, the ship runs the risk of damaging its hull on the sea bottom. The draft of the ship, the distance the hull extends below the surface, is equal to the interior width of the ships hull. Damage from running aground can never exceed 10% of the ship's HPs. Ships that run aground do not sink, they become obstacles that must be manoeuvred around. Reefs have a specific area they cover and a specific depth. The depth may vary along the length of the reef. The damage is taken when the bow of the vessel crosses the edge of the reef and is not taken again unless the ship leaves and then reenters the reef. Reefs do 2 damage to a hull along its entire length. 

Rubble - This consists of all manner of stone, wood, animal, plant and artificially-made debris that have gathered into large tangled piles on the beach. Rubble can exist both above and below the water.

Sand - This is either soft, dry sand or wet sand that has been recently churned up and not allowed to settle. If underwater, characters can swim over them without penalty.

Tide changes proceed via the following stages:
Sea level rises over several hours, covering the intertidal zone; flood tide.
The water rises to its highest level, reaching high tide.
Sea level falls over several hours, revealing the intertidal zone; ebb tide.
The water stops falling, reaching low tide.
Tides produce oscillating currents known as tidal streams. The moment that the tidal current ceases is called slack water or slack tide. The tide then reverses direction and is said to be turning. Slack water usually occurs near high water and low water. But there are locations where the moments of slack tide differ significantly from those of high and low water.

Tsunamis have a small amplitude (wave height) offshore, and a very long wavelength (often hundreds of kilometres long, whereas normal ocean waves have a wavelength of only 30 or 40 metres), which is why they generally pass unnoticed at sea, forming only a slight swell usually about 300 millimetres above the normal sea surface. They grow in height when they reach shallower water, in a wave shoaling process described below. A tsunami can occur in any tidal state and even at low tide can still inundate coastal areas. While everyday wind waves have a wavelength (from crest to crest) of about 100 metres and a height of roughly 2 metres, a tsunami in the deep ocean has a much larger wavelength of up to 200 kilometres. Such a wave travels at well over 800 kilometres per hour, but owing to the enormous wavelength the wave oscillation at any given point takes 20 or 30 minutes to complete a cycle and has an amplitude of only about 1 metre. This makes tsunamis difficult to detect over deep water, where ships are unable to feel their passage. As the tsunami approaches the coast and the waters become shallow, wave shoaling compresses the wave and its speed decreases below 80 kilometres per hour. Its wavelength diminishes to less than 20 kilometres and its amplitude grows enormously. Since the wave still has the same very long period, the tsunami may take minutes to reach full height. Except for the very largest tsunamis, the approaching wave does not break, but rather appears like a fast-moving tidal bore. Open bays and coastlines adjacent to very deep water may shape the tsunami further into a step-like wave with a steep-breaking front. When the tsunami's wave peak reaches the shore, the resulting temporary rise in sea level is termed run up. A large tsunami may feature multiple waves arriving over a period of hours, with significant time between the wave crests. The first wave to reach the shore may not have the highest run up. About 80% of tsunamis occur in the Pacific Ocean, but they are possible wherever there are large bodies of water, including lakes.

Major Pacific trenches (1-10) and fracture zones (11-20): 1. Kermadec 2. Tonga 3. Bougainville 4. Mariana 5. Izu-Ogasawara 6. Japan 7. Kuril–Kamchatka 8. Aleutian 9. Middle America 10. Peru-Chile 11. Mendocino 12. Murray 13. Molokai 14. Clarion 15. Clipperton 16. Challenger 17. Eltanin 18. Udintsev 19. East Pacific Rise (S-shaped) 20. Nazca Ridge

The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor. Oceanic trenches are a distinctive morphological feature of convergent plate boundaries. Along convergent plate boundaries, plates move together at rates that vary from a few mm to over ten cm per year. Trenches are generally parallel to a volcanic island arc, and about 200 kms from a volcanic arc. Oceanic trenches typically extend 3 to 4 kms below the level of the surrounding oceanic floor. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 11,034 metres below sea level.

MetaTech

The Ocean Belles

The Prometheus Institute

The Throne of Streams

Emission Hydrokinetic

Emission Hydrokinetic Sphere

Emission Ice Cage

Field Hydrokinetic

Flight Hydrokinetic

Flight Hydrokinetic II

Hydrokinesis

Hydroportation

Infuse Weapon Hydrokinetic

Metamorph Ice

Metamorph Liquid