* Sea-horse: A small, bony fish with a horse-like head
* Sea-lion: A large, marine mammal that is related to seals
* Sea-turtle: A turtle that lives in the sea
* Sea-urchin: A spiny, marine invertebrate
* Sea-anemone: A colorful, flower-like marine animal
* Sea-slug: A soft-bodied, marine mollusk
* Starfish: A marine animal with five or more arms
* Jellyfish: A free-swimming marine animal with a bell-shaped body
* Seahorse: This one is a single word, but it is also a compound word in origin.
Let me know if you'd like more examples!