1. Dolphins are highly intelligent and social mammals that inhabit oceans and rivers. They are known for their playful behavior and complex communication skills.
2. Whales are the largest animals on Earth, and they live exclusively in the hydrosphere. There are various species of whales, including the blue whale, the humpback whale, and the killer whale.
3. Seals are semi-aquatic mammals that can live both in water and on land. They have streamlined bodies and flippers that help them swim efficiently in the ocean.
4. Sea turtles are marine reptiles that inhabit the world's oceans. They have hard shells that protect them from predators and help them float while swimming.
5. Manatees and Dugongs are large aquatic mammals that feed on seagrass. They are found in warm waters in coastal areas and estuaries.
6. Sea otters are marine mammals that live in kelp forests along the Pacific coast of North America. They are known for their dense fur and their playful behavior.
7. Fish: There are a vast diversity of fish species that live in the hydrosphere, ranging from small colorful reef fish to large predatory sharks.
8. Squids: Squids are cephalopods found in all oceans. They have a unique anatomy, with a mantle, ten arms, and a beak, and are capable of rapid movement through jet propulsion.
9. Jellyfish: Jellyfish are gelatinous zooplankton that drift through the water column. They have a radial symmetry and a bell-shaped body, and use their tentacles to capture prey.
10. Coral: Corals are marine invertebrates that build intricate structures called coral reefs. They are important for marine biodiversity and provide shelter and food for various organisms.