Semi-aquatic mammal

This is a list of tetrapods that spend part of their life cycle or a significant fraction of their time in water.

Semiaquatic Tetrapoda are those that are primarily or partly but that spend a large amount of time swimming or otherwise occupied in water, either as part of their life cycle or as an essential behavior (e.g. feeding). Some marine mammals, such the marine otter, the polar bear and pinnipeds, are semiaquatic, while others, such as the sea otter, cetaceans and sirenians, are fully aquatic. The only fully aquatic nonmarine mammals are several manatees (the Amazonian manatee and some populations of African manatee) and certain small cetaceans (river dolphins, the tucuxi, and some populations of Irrawaddy dolphin and finless porpoise). Among marine reptiles, marine iguanas and partly marine crocodiles (such as the saltwater crocodile and the American crocodile) are all semiaquatic. Sea turtles are almost fully aquatic, but must come ashore to lay eggs. Most sea snakes are ovoviviparous and fully aquatic (the exception being the oviparous, semiaquatic sea kraits). On the other hand, no bird species is fully aquatic, as all must lay and incubate their eggs, as well as begin raising their young, on land or ice. Most amphibians have an aquatic larval stage and are at least semiaquatic for that reason, but there are many exceptions to this generalization.

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