Aquatic ape hypothesis - Wikipedia
I read a book years ago in my freshman year in college, it was a physical anthro course, the author was Elaine Morgan.
She posited that modern humans have they're beginnings in a beach and water environment.
Did some other primate inhabit the water? Good question, except the fossil record as of yet does not seem to support it.
The Savannah grassland theory still seems to be the accepted theory of where primates began the journey to humanity.
"You were not there for the beginning. You will not be there for the end. Your knowledge of what is going on can only be superficial and relative" William S. Burroughs