Anthropology

The aquatic ape hypothesis (AAH), also referred to as aquatic ape theory (AAT) and more recently the waterside model, is the idea that certain ancestors of modern humans were more aquatic than other great apes and even many modern humans, and, as such, were habitual waders, swimmers and divers. The hypothesis in its present form was proposed by the marine biologist Alister Hardy in 1960, who argued that a branch of apes was forced by competition over terrestrial habitats to hunt for food such as shellfish on the sea shore and sea bed leading to adaptations that explained distinctive characteristics of modern humans such as functional hairlessness and bipedalism.

https://en.wikipedia.org/wiki/Aquatic_ape_hypothesis