What is a false start and what happens if I cause one?

A boat crossing the start line after the Starter has raised the Start Flag (or the red light is shown) but before the start is given has committed a false start. If more than one boat crosses, only the crew or crews the Judge at the Start decides actually caused it are penalized. The Starter stops the race with a horn or audible device and a waving red flag, and when the crew has returned to its starting position awards a Yellow Card: "(Name of Crew), False Start, Yellow Card." The Yellow Card stays in effect until the race has been rowed, including after a postponement or re-row. A crew with two Yellow Cards is excluded from the race, and the Starter tells it when and how to leave the start area (rule 10.7).