From my reading of the situation (having been converted), it seems that being a 'just so' explanation (not so evidence based, just conjecture), and one put forward by a woman in the 1970s, it was met with really over the top hostility for what I think is an interesting hypothesis.
You get into how our fingers prune up for better grip in the water, our diving reflex, and how at-home some spearfishers and free divers are in the ocean, not to mention the multitude of fishing villages that predate written history by who knows how long... it's a very convenient explanation -- which academics are right to be skeptical of -- but I don't think it deserves being cast as bunk.
Somewhat tangential, but here's my favorite video of humans being at home in the ocean, "Living off the Land in Hawaii", with badass laying on the ocean floor waiting for a meal @3:45 https://youtu.be/jJXEepvG6Hc?t=225