Most top swimmers use the grab start to get their race under way. This gets you moving off the blocks quickly and into the water smoothly. The starter will not begin the race until everybody is ready and still. This is really important because you can be disqualified if you fall in before the start or if you are slow getting ready. Follow along in this how-to animation to learn the best method to power off the blocks in swimming.
The better your starting position, the better your dive, so:
Head: Tucked in as close to your knees as possible
Hips: As high as possible, lift them up and try not to push them back
Legs: Curl your toes over the edge of the block and bend your knees slightly
Arms: Should be in a "hands on" position, this means one hand on top of the other. Stretch your arms down, point your fingers to the floor and put your palms on the front of the wall or starting block.
Push off with as much power as possible. Press hard with the palms of your hands and throw your arms forward. Look up slightly as you push away to get your body to follow your head. If you look up for too long, however, your feet will go in at the same time as your hands. This is not a good idea.
As soon as your feet leave the starting block:
1) Tuck your head in
2) Push your hips up
3) Streamline your body so that you go into the water head first
As you approach the water, imagine you are trying to slide through a hole without making any splash. As you go in, let your hands and head lift slightly. Try to hold the "hands on" streamlined position until you are close to the surface and ready to start swimming. A really good tip for making a smooth change from diving to swimming is to imagine that there is no join between the two. Someone watching should not be able to see where one finished and the next one started.