Photo: Jessica Steiger, winner of the 2016 Butterfly skins event with runner up Kirsty Simpson.
The fastest eight swimmers from the open 50m heats progress to the final in the evening session.
All eight compete in the first round, after which the slowest two are eliminated. In the second round the slowest two are again eliminated. There are three more rounds with the slowest swimmer eliminated in each round until a winner is left. The swimmers are eliminated as follows:
Round 1 : – from 8 to 6 swimmers
Round 2 : – from 6 to 4
Round 3 : – from 4 to 3
Round 4 : – from 3 to 2
Round 5 : – the final 2 go head to head to produce a winner.
Round one is seeded as a final. Surviving swimmers from each round remain in their allocated lanes throughout until only two remain; in the final round the last two swimmers compete in lanes 4 and 5.
Round one starts under normal starting procedures. Only times set in round one count as accredited times for future events. Rounds 2- 5 start at three minute intervals.
For rounds 2-5, the starter gives a warning whistle 10 seconds prior to the next start. The signal to start will then sound without any verbal commands.
Swimmers starting before the starting signal or breaching the stroke rules will be disqualified with all remaining swimmers progressing to the next round. Where there are two or more disqualifications in any single round, elimination of the swimmer finishing last will be suspended until the number of disqualifications are accounted for, ensuring that 5 rounds will be completed.
FINA start and stroke rules apply to all starts and strokes.
The men’s and women’s event will alternate each evening. This will give the effect of a leg starting every 90 seconds.