All mammals are born with the innate ability to swim. Deer, dogs, Guinea pigs, real pigs… all strong swimmers right out of the womb. Well, all mammals but apes. They will all drown unless taught; humans, chimpanzees, and Orangutans have been shown to be capable.
Gorillas are unknown, but since no documentation of humans teaching one exists, it is theorized that no Gorilla has ever successfully swam (they don’t live near oceans, and have never been seen in deep water).
Additionally, giraffes are theorized to be possibly able to swim, though not very well. They also have never been seen in deep water, and their body shape puts their success into question.