Just looking at his stroke, it looks to me that he is doing the "I" stroke, the hand following the line on the bottom of the pool? An "S" but it is an "S" if you count his body rotation.
Just looking at his stroke, it looks to me that he is doing the "I" stroke, the hand following the line on the bottom of the pool? An "S" but it is an "S" if you count his body rotation.