Fish

When we say fish, we generally imply anything that lives in water. But the dictionary defines fish as - any of various cold-blooded aquatic vertebrates having gills, commonly fins and typically an elongated body covered with scales. Now this definition excludes a lot of sea animals.

Dungongs

whales

Whales and dungongs come from a lineage of land animals. So there were some creatures that emerged from the sea to land, which was a major evolutionary step, and some who went back to the sea after their shortlived land habitation. Seals and Sea lions have only gone part-way back. But whales (including the small whales we call dolphins) and dungongs with their close cousins the manatees, ceased to be land creatures altogether and reverted to the full marine habits of their remote ancestors. But they do, however, still breathe air, having never developed anything equivalent to the gills of their earlier marine progenitors. Other animals that have returned from land to water, at least some of the time, are pond snails, water spiders, water beetles, crocodiles, otters, sea snakes, water shrews, Galapagos flightless cormorants, Galapagos marine iguanas, yapoks, platypuses, penguins and turtles.

Instead of spinning regular silk webs, they form platicy, silky air bubbles on the surface of water