No floaties required. Researchers now have the first video evidence that apes can learn to swim and dive. Like humans, wild apes exposed to deep water will fumble and flail. Our uncoordinated movements bear little resemblance to the tried-and-true doggy paddle that most other mammals use instinctively. But a chimpanzee named Cooper and an orangutan named Suryia, both raised in captivity and regularly exposed to bathtubs and swimming pools, developed unexpected underwater skill. Reassured by the presence of a safety rope, Cooper became increasingly adventurous over a period of days: He could tread water, submerge himself (with eyes shut tight), and propel himself with a kick reminiscent of the human breaststroke. Suryia (shown in the video above) also opted for a breaststroke-esque kick, but took his skills a step further, opening his eyes underwater and traveling up to 4 meters while submerged for as long as 15 seconds. In a report this week in the American Journal of Physical Anthropology, researchers offer an evolutionary explanation: When an early ancestor of modern apes took to the trees, they say, innate swimming ability likely lost its advantage, and the trait disappeared. The fact that our muscles and brains adapted to graceful swinging movements in the air and upright walking on the ground might account for the lengthwise reaching and pulling movements that define Cooper and Suryia’s aquatic style.