Types of aquatic animals include marine mammals such as whales, dolphins, sea lions, seals, manatees and walruses. Other types are fish, including bony fish such as groupers and cartilaginous fish such as sharks and rays. Invertebrate aquatic animals include sponges, corals, sea stars, sea anemones, sea urchins and sea cucumbers. Other examples include sand dollars, jellyfish and colony animals such as the Portuguese man-of-war, marine worms, clams, mussels and barnacles.
Other aquatic animals include scallops, limpets, sea snails, squid, octopuses, cuttlefish, crabs, lobsters and shrimp. Aquatic birds include penguins and aquatic insects include water boatmen. The nymphs or larvae of otherwise terrestrial insects such as dragonflies and mosquitoes are aquatic.
Other aquatic animals are sea snakes and sea turtles, and there's even an aquatic spider. This spider builds a web on the surface of the water and fills it with air bubbles. It even encases its abdomen in a bubble of air that allows it to stay underwater much of the time.
The Portuguese man-of-war looks like a jellyfish, but it's not. It's actually a colony of four organisms. One is a bladder that's full of gas and floats on top of the water, a second digests the food, another is responsible for reproduction and the fourth makes up the long tentacles that trail beneath the float.