I'm not buying that. Even if it is at steam sale with 90% off.

First: As far as I know, the most direct human ascendances (being the first one the one that diverged from chimps) were basically primates that lived mainly in savannah enviroments in Africa (with the exception of the some species, and even then, none were aquatic/semiaquatic) and there is a whole fossil record to prove this .In fact, I doubt that any Primate species does live in the water even as much as other semiaquatic mammals.

Second: Fat in those animals (specially in cetaceans) is a sustitute of fur, since fur wouldn't be an effective heat aislant if you spend pretty much your entire life underwater. And even then, sea lions,otters… still have some fur.

Third: Fat IS healthy, an abnormal percentage of it isn't (well, duh!). And that's is the case of every other mammal (and I would even say vertebrate).

Etc.

Trying to use evolution (specially doubtful HYPOTHESIS of evolution) to justify fat pride is one of the most bizarre things I have read, and one of the dumbest things I've ever read too.