Modelengine mobs:
Beluga:
eats all kinds of small fish, demands food if you hold salmon in your hand
Narwhal:
eats all kinds of small fish, demands food if you hold salmon in your hand
Great whale:
jumps above water with splash, occasionally squirts water out of blowhole above surface
Octopus:
hunts crabs and shells, squirts ink if attacked

Single Entity Item Mobs:(all of these are usable as statues and trophies)
King crab:
seabed creature, salvages corpses
Dogfish:
harmless small shark, food for others
Moon jellyfish:
spawn in groups, change model on each hit less jellies, emissive, harmless
Sunfish:
peaceful inhabitant, hunts jellyfish
Sea urchin:
seabed animal, emissive
Barnacle:
spawns on rock, seabed inhabitant

Loot items:
small, large and medium fish meat
pile of shells
whale meat
pincer
crab meat
narwhal horn
tentacle