What is the start procedure for backstroke and medley relays?

Backstroke races and medley relays start in the water (World Aquatics rules, Part Two, Article 4.2):

1. Once swimmers have removed all clothing except swimwear, the Referee gives a short series of whistles to call them to the starting end.
2. A first long whistle: swimmers must immediately enter the water.
3. A second long whistle: swimmers return without undue delay to the starting position (facing the wall, hands on the grips).
4. When swimmers and officials are ready, the Referee holds out an arm towards the Starter. The swimmers are now under the Starter's control, and the arm stays out until the signal.
5. When all swimmers are in position, the Starter says "take your marks".
6. When all swimmers are stationary, the Starter gives the starting signal.