In Rowing, the shells (boats) are held at the starting dock to ensure they are straight and that no boat has a starting advantage. Each boat is allowed one false start. A second false start by the same boat results in disqualification of that boat and crew.
This photo features the men's single sculls event which is signified by the symbols (1x). A scull is a boat that is propelled by the use of an oar in each hand.