Apart from baboons wading in intertidal rockpools for food and capuchins foraging in mangroves at low tide, very few primates other than humans actually swim well or regularly.
There are two exceptions, though. First, proboscis monkeys, which leap from branches high up over rivers and plunge into the slow-flowing water beneath, where they are able to swim up to 20m below the surface; and second, the crab-eating macaques from Indonesia.
These are expert aquatic primates, swimming underwater with their eyes open in search of shellfish and fruits that fall from the trees overhanging the rivers in their jungle home. They are capable of holding their breath for up to 30 seconds. There is also a theory (which has been widely discredited) that states that human ancestors passed through an aquatic stage, which accounts for our bipedal (two-legged) movement and lack of dense body hair.
Main image: A proboscis monkey swimming © Getty Images
