Hippos don't technically know how to swim. The perfect combination of buoyancy and bone density allows them to "fly" through water at speeds of 5 mph (8 kph) propelling themselves using intermittent contact with the ground, like astronauts on a moonwalk.
https://nostr.build/av/113287949a8cf7af14a80e38d17a02adc61a47694d4d41344787b4c24080f1dd.mp4