Phasing and sequencing kick
At this slowtwitch forum thread Gary Hall has a very interesting question that he poses: where is the most powerful point in the underwater pull?
I won’t try to recap all the conversation, but the first three pages have some very interesting commentary on swimming theory and several research studies. There is also some interesting information about phasing and sequencing of the kick and the pull. Hit the link and take a quick read. It’s especially interesting if you enjoy the physics theory behind swimming.