Depends on what you mean by live underwater.
Whales, manatees and dolphins are all mammals that live their whole life mostly underwater. They are still air-breathing though, so they have to surface veryregularly to breathe.
No animal mammal can live entirely underwater.
Us humans could potentially live entirely underwater by using technology to bring some surface conditions(=breathable air) with us into the depths.
A plant-eating mammal that lives under the sea is commonly known as a sea cow or a manatee.
There are a number of species of aquatic mammals, including whales, seals, and dolphins.
Coatimundi
haha nice question. its a whale. or maybe a shark.
A marine mammal found in the water around Australia would be the dugong.
Otter.
The scientific or taxonomic name would be Bubalus spp.
a bear
some of the names of animals that lives in water are frog, crocodile, hippopotamus and turtle.
Remoras
a water shrew obviously lives in water. I says it in the name.
Venice