Swimmers (All Tomorrows)

The Swimmers were many of the posthuman species created by the Qu from a colony of the Star People. They were all domesticated and had to be taken care by special attendants.

Diverse forms of swimmers included eel-people, huge, whale like behemoths, decorative people who swam by squirting water out of their hypertrophied mouths and horrifying multitudes of brainless wallowers that served as food stock were put on an ocean planet. All of them went extinct when the Qu left.

Swimmers (All Tomorrows)

    The only species of swimmers that survived were a few forms that were        only slightly mutated and resembled their human ancestors to some                degree. They had no artificial gills, hand-like flippers, and their hind              flippers were still paired like the legs of their ancestors. Even though they      didn't understand each other in any sapient way, they spoke to each other.

    Over thousands of years, they evolved more streamlined forms and                became better and better hunters of fish. It took them a really long time to      found a civilization again, but eventually they managed to domesticate          some aquatic organisms and became the Tool Breeders.

Source: WikiFandom