Demersal

When you want to call someone a bottom-dwelling scum, but you want to veil it in langauge they won't understand.
periphyton - sessile organisms, such as algae and small crustaceans, that live attached to surfaces projecting from the bottom of a freshwater aquatic environment.
sapropel - An aquatic sludge-like sediment rich in organic matter formed in oxygen-free areas at the bottom of lakes
demersal - that lives near the bottom of a body of water
limicoline - shore-dwelling