For many years, zoos have used water moats to confine chimpanzees, gorillas or orangutans. When apes ventured into deep water, they often drowned. Some argued that this indicated a definitive difference between humans and apes: people enjoy the water and are able to learn to swim, while apes prefer to stay on dry land.

Renato Bender from the University of the Witwatersrand, Johannesburg and Nicole Bender from the University of Bern have studied a chimpanzee and an orangutan in the United States.

These primates – Cooper the chimp and Suryia the orangutan – were raised and cared for by humans and have learned to swim and to dive.