a crab

a crayfish

a dolphin

an eel

a hammer fish

a jellyfish

a lobster

a manatee

a mussel

an octopus

an orca

(also a killer whale)

an oyster

a prawn

a ray

a sawfish

a scallop

a sea anemone

a sea lion

a sea turtle

a sea urchin

a seahorse

a seal

a shark

a squid

a starfish

a swordfish

a walrus

a whale