"Water Ballet" at the Olympics

From the International Olympic Committee website on Synchronized Swimming:

...Most importantly, an underwater speaker lets the swimmers hear the music clearly while underwater, helping them achieve the split-second timing critical to synchronised swimming.

Originally known as water ballet, synchronized swimming began in Canada in the 1920s. It spread to the United States in the early '30s, where a display at the 1934 Chicago World's Fair drew rave reviews. Its popularity soared further when Esther Williams performed in a string of MGM "aqua musicals" in the 1940s and '50s...

Click here for a neat interactive flash demonstration of the sport.