Fish fishes underwater sealife ocean sea water 115. Mantle length ml is the standard size measure for coleoid cephalopods shell diameter being more common for nautiluses and is almost universally reported in the scientific literaturethe mantle is the cephalopods body lying posterior to the head and enclosing the visceral mass and mantle cavity the latter being used for locomotion by jet propulsion. Of water some time in the 1980s along a cavernous reef system. Ship wreck the catherine or the kathryn caverns just 10 minutes this is an old minesweeper which was sunk in 50 ft. A marine biologist is someone who works in some branch of marine biologygiven that around 70 percent of the earths surface is covered in oceans you can imagine that marine biology is a very large field encompassing everything from studies of ocean currents to analysis of the creatures who live next to hydrothermal vents.