The object is to keep your head out of water, and your eye on the victim. Step into the water with one foot --legs spread far as possible, taking a long stride . If you jump first, you'll bring your legs together in mid-air. When the water reaches your waist, scissor kick your legs together. Then hold your arms straight out at your sides, level with the horizon & bring them down to your waist , to help slow your body's descent into the water. Add the jump towards the victim, more out than up. Keep your feet wide apart . Don't try to swim. Make as big a splash as possible. There will be plenty of time to stroke to the victim, but it's more important to not lose sight of the victim.
It is not necessary that a stride jump is only related with swimming, but basically a stride jump is the jump in which the doer maintains the take off position for as long as possible. When the jumper comes into land then he takes off leg join the free leg for getting a good landing position. It needs practice and learning lessons, and for complete details click on the link:
stride jump
stride jump