There are many sea animals with four letters, including:
- Crab: A crustacean with a hard shell and two claws.
- Eel: An elongated fish with no scales.
- Frog: An amphibian that lives both in water and on land.
- Koi: A colorful ornamental fish of the carp family.
- Ray: A cartilaginous fish with a flattened body and a long tail.
- Shark: A carnivorous fish with a cartilaginous skeleton and sharp teeth.
- Shrimp: A crustacean with a long, slender body and two pairs of antennae.
- Squid: A cephalopod with a soft body, eight arms, and two tentacles.
- Toad: An amphibian with a warty skin and short legs.
- Whale: A large marine mammal with a streamlined body and a tail fluke.
These are just a few examples, and there are many other sea animals with four letters.