Dangerous:

Sea snakes- typically these would not be threatening due to their mouths being too small to bite humans, but you're shrunk, so I believe you're out of luck.

Coconut Crabs: Don't let the name fool you. These crabs have claws and are territorial.

Rats: They are territorial and may chase and bite you.

Pelicans: It's possible that they could mistake you for a fish.

Seagulls: They eat anything.

Normal crabs: extremely territorial, will kill but not eat.

Ants: they will attack in packs

Bees: will attack if you seem threatening

Spiders: I'll let you use your imagination

Possibly threatening:

Chickens: they can be vicious around their chicks

Cats: might think you're a mouse or bird

Dogs: might think you're a mouse.

Neutral:

Mice (I think)

Cockroaches: unless there's a swarm

Small lizards: The marine iguanas are a problem, but not these guys

Pigs

Cows: unless they step on you

Possible allies:

Cats

Dogs

Guinea Pigs

Snails