Being able to focus on one specific aspect of your stroke sometimes takes isolation. Swimming underwater certainly gives you that.
Why Do It:
Swimming under water takes away all other aspects or worry about balance or breathing so you can focus just on how your arm connects with the water.
How to Do It:
1. Push off deep under water, and start swimming freestyle.
2. Rotate your body enough to really catch the water as you pull.
3. During the recovery, you’ll discover the best way to get your hand back in front.
4. You’ll need to keep a constant kick going to keep moving while you create resistance in the recovery.
How to Do It Really Well (the Fine Points):
When you focus intently on the catch, your body should rotate to a point that looks exactly like you’d want it to while swimming good freestyle. Transition from under water swimming, to full-stroke freestyle by gradually rising to the surface. Breath control will be important on this one.