The curvilinear path in elite swimming is not an illusion caused by body rotation or elbow flexion. It’s undeniably present in the world’s fastest swimmers.
Vladimir Morozov swims freestyle uses a straight-arm technique. See an underwater photo of his stroke from Swim Speed Strokes.
Because of the feedback we’ve gotten on Facebook, I will offer a short explanation of what I mean by “S-pull” and how all elite swimmers today show it in their stroke.
After getting many comments about this post on Facebook, Sheila Taormina has written a response that more fully explains the S pull in swimming in this new post: Let’s Talk About the S Pull in Swimming.