Physics tells us that when diving in or pushing off the wall you are going faster than you can swim. The purpose of underwaters is to maintain that momentum.

Finding power underwater starts with your body position off the blocks or off of the wall. Streamline is crucial to maximizing your in water propulsion. Engaging your core off the block or through each turn will help keep you in proper position and stop slow down from side to side sway or drag. Stretch out and extend your reach through the water. That will stop the 'body position shrink' many swimmers experience. Long straight posture will bring more speed off the start and the wall as well as each turn. Your body should undulate through the water in a wave like motion. Don't forget dolphin kick starts at the hip.