Flipturn

A tumble turn or flip turn is one of the turns in swimming, used to reverse the direction in which the person is swimming. It is done when the swimmer reaches the end of the swimming pool but still has one or more lengths to swim.

The technique's development is credited, by the International Swimming Hall of Fame, to Al Vande Weghe at the AAU Nationals in 1934. Previously this entry erroneously credited the invention of the flip turn to University of Texas swim coach Tex Robertson while he was training Adolph Kiefer for the 1936 Olympics.

Flip turns are only permitted during freestyle and backstroke races. In butterfly and breaststroke races, regulations require swimmers to touch the end of the pool with both hands simultaneously before turning back for another length. This style of turning is called an open turn.

If the event is medley swimming turns vary based on the combination order of what stroke the swimmer is changing from and to. According to the USA Swimming Stroke and Turn Regulations, in order of the strokes the turns are to be:

...
Wikipedia