Platform Diving (Synchronized)
From the Super Mario Wiki
Platform Diving (Synchronized) is an Aquatics Event that exclusively appears in the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The objective of the event is to score the most points by jumping off the diving platform with the best timing. The starting record for the event is 91.0pt(s).
For this event, the player must select two characters from the Tricksters category and will compete against a pairing of the other two as well as two Koopa Troopas and a pair of Chao, however in the story mode version the player only competes against Dr. Eggman and Metal Sonic. At the start of the event, the player will be given a number of seconds that they have to count without a timer before they perform the dive. The characters will walk to the edge of the platform and prepare to dive, with a timer showing when the player needs to count from. The clock then disappears and the player must count for the specified amount of time, and press A once they think the time has passed, causing their characters to perform the dive. The player will then be told when they pressed A and how long off of the specified time they were and are then given a score based on their timing. The further from the time their button press, the lower the score, but it does not matter whether they pressed the button early or late, as an equal score would be given for being one second early or late.
1) Dive: Press the A Button.