Fish:
* Bony Fish: Salmon, tuna, cod, seahorses, clownfish, etc.
* Cartilaginous Fish: Sharks, rays, skates
* Jawless Fish: Lampreys, hagfish
Mammals:
* Whales: Blue whales, humpback whales, orcas (killer whales), dolphins, porpoises
* Seals: Harbor seals, elephant seals, fur seals
* Sea Lions: California sea lions, Steller sea lions
* Walruses:
* Manatees:
* Dugongs:
Reptiles:
* Sea Turtles: Leatherback turtles, green sea turtles, loggerhead turtles
* Sea Snakes:
Invertebrates:
* Crustaceans: Crabs, lobsters, shrimp, barnacles
* Mollusks: Oysters, clams, mussels, squid, octopus, snails
* Echinoderms: Starfish, sea urchins, sea cucumbers
* Cnidarians: Jellyfish, corals, sea anemones
* Sponges:
* Worms: Polychaete worms, flatworms
Other:
* Seabirds: Albatrosses, penguins, gulls, petrels
* Marine Insects: Water striders, sea skaters
Things to remember:
* Marine life varies drastically depending on location: Different types of animals live in the open ocean, coral reefs, deep sea vents, and shallow coastal waters.
* New species are constantly being discovered: Our understanding of the ocean is always evolving.
I hope this gives you a good starting point!