100m Freestyle (Mario & Sonic at the London 2012 Olympic Games for 3DS)
From the Super Mario Wiki
100m Freestyle is an Event that appears in the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The aim of the event is to swim the distance in the fastest time possible. The starting world record for this event is 46.91, and the starting Olympic record is 47.05.
In the game's story mode, 100m Freestyle appears as the first challenge of Heroes Episode 1, Mario and Sonic, in which Mario must beat Fog Imposters of Luigi, Sonic and Tails, and also as the fifth challenge of Heroes Episode 3, A Rainbow in Fog, in which Mario must once again beat Fog Imposters of Luigi, Sonic and Tails. It also appears as part of the third challenge of Heroes Episode 5, The Promise to Toad, in which Mario must beat Fog Imposters of Luigi, Sonic and Tails again in it as well as in 100m and Marathon.
The event starts on the final fifty metres of the swim after 24 seconds have elapsed, with the time and the remaining metres displayed constantly throughout the event. The player must tap alternately on the left and right sides of the touch screen to cause their character to kick. Their character's speed is increased by tapping faster. A meter is displayed onscreen which indicates how fast the player is tapping on the screen. If the player taps too fast and their speed passes the end of the meter, their character will overheat and will stop briefly. If the player manages to keep their speed within the green section at the end of the meter, their character will perform a special move at intervals which boosts them further. Keeping the speed under the green section has no effect.
1) Swim: Tap left and right alternately on the Touch Screen.