Like most things in swimming, backs starts have evolved through the years. Though it all there has been one constant- backstroke starts in the water. The basics of the start are simple:
Get a good grip on the bar below the starting block.
Position your feet against the wall shoulder's width apart.
Relax your neck and drop your chin- so that you are looking at your knees.
Here are a few more tips to consider.
Use Hip & Knee Extension to drive off the wall. Extending your hips and knees helps you explode during push-off. Remember a start is a jump! Velocity drives you into the water.
Don't Forget To Push With Your Arms. Back starts have two points of contact for pushing the body out of the water.
Clean Entry. A combination of factors: streamlined arms, arched back, high hips, and pointed toes create a clean entry. By arching your back your transferring energy created from the start into your kick.