Often the most misunderstood part about swimming is the initial part, The Catch. The catch is important to setting up the rest of your stroke. Important because a poor catch makes swimming harder and increases the odds of going nowhere fast. When I coached swimmers, this was the hardest part of the stroke to teach someone, it depends upon feel of the water, kinesthetic awareness and a bit of knowledge of what the initial part of your propulsive phase does and where it should begin. The Catch is subtle and happens before most can think about what they are doing to catch the water.
To catch the water, you need to get the entry correct. The hand should enter the water well in front of the head, more or less inline with the shoulder and extend a bit. Your elbow should be rotated towards the wall and there should be a small bend in the elbow. Contrary to popular belief you do not have to reach as far forward as you can. Reaching that far forward will cause your elbow to rotate down towards the bottom making the catch a bit more difficult if not nearly impossible to do properly. Entering properly will help you avoid injury and set up the next part of the swim stroke – The Catch.
The correct way to catch the water is to enter the water, extend your arm and leave a small bend in the elbow. Remember, full extension will cause the elbow to drop and dropped elbows are not conducive to swimming fast. Your elbow should be rotated towards the wall, palm facing down or rotated slightly toward the midline of your body. Extend from your shoulder allowing your hand to drop just a bit, an inch or two at most. You are not pushing your hand down or back, but allowing the hand to drift down. Your elbow will float up so that it is higher than your hand. It should still be rotated out. Once your elbow is above your hand you can press the hand down by flexing the wrist slightly. If you flex too much you will actually catch more water initially but you will not be able to hold as much water throughout the rest of your stroke. Once you have flexed the wrist slightly, keep the elbow up and the shoulder pushed forward then start moving the forearm and hand down and back towards the wall behind you. You have caught the water and are transitioning into the next phase of your swim stroke.