4) Hand and shoulder control
The Blunder: Your shoulders are not in optimal position for a long, forward reach and/or your hands are not in optimal “paddle” position.
Why it’s a blunder: Reaching forward and pulling through with a long, effective stroke is the key to swimming efficiently. When you’re too tight in the upper torso you are limiting your reach while creating more side-to-side movement than you are forward (more explanation below).
The other blunder concerns your hand. When you pull through and complete your stroke, your hand needs to be in the most effective position to grip the water and displace it. Having your hand either cupped or your fingers completely spread apart means you’re not creating the optimal surface area to propel yourself forward.
The Fix: The swimmer in the bottom of the picture below has her shoulders level and squared (not to mention she is also overreaching!) and is not getting a full reach forward. Compare with the swimmer in the top of the picture, who is getting a full extension. The extended shoulder is in front of the other one, leading the way.
Position your hand like the swimmer on the right: thumb out to the side with the other four fingers together. You don’t need to squeeze them together either, as studies have shown that small gaps between fingers don’t result in meaningful loss in swim and stroke efficiency. Not to mention, this will give you a hand cramp.