One that don’t get eaten

I'm a beluga whale in the morning, a siren at night

Shark

Kraken

Otter. They are fast, fresh water, have sharp little teeth, good hunters, and they are cute and playful.

Something with some type of defense mechanism, like a stingray or a jellyfish.

Something beautiful but barely sentient.

I think I would go with dolphin too.🐬

Either lobster or angler fish

Chironex Fleckeri aka sea wasp aka extremely venomous box jellyfish.

Octopus

Orca

A killer whale:

No dieting and always dressed for formal occasions.

I want a giant seahorse

I oughter be an otter

Bull shark.

Octopus