Crossing the Centerline
This swimmer crosses the centerline twice for each arm stroke. Somebody
told her to "Make the letter S with your hand." Don't
listen to these people! It's like swishing a paddle back and forth sideways
in the water. It doesn't do much to move you forward.
In the upper sequence, her left hand enters at a sharp angle and slices
across the centerline. This is a serious braking action for both that
hand and her body. In the first shot her body is heading directly at the
camera, but you can see that she is veering to the left in the third shot.
The weight and velocity of your hand and arm entering the water represents
potential energy, and it's a shame to waste it veering to the side, when
it could be put to much better use being dropped straight ahead, providing
The second sequence is a continuation of the first. The swimmer sculls
her left hand back out to the side (and deep) to catch, then pulls back
under her body and across the centerline again, and finally she sculls
to the outside again to end the stroke.
The hand and forearm are slipping this way and that, and not providing
a very good hold on the water.