Turtle: "Some physical aspects don't make much sense otherwise - our bodily hair, our reliance on bodily fat for insulation, our relatively good aquatic streamlining compared to apes..."
Nothing said about "long and skinny", just streamlining. You distorted his meaning, perhaps accidentally. Blubbery round walruses are streamlined, long and skinny ostriches are not. Gibbons are by far much longer and skinnier proportionately than humans, and they almost never get near water and are not well streamlined. Human babies are far rounder than any apes or monkeys. Underwater, various sagging fat deposits tend to be equally pressurized on all sides, unlike on dry ground where gravity pulls everything downwards, so even a diver with a beer gut tends to become more cylindrical and hydrodynamic. As far as female breasts, I think it is very likely that archaic human females had less pendulous protruding breasts, with a wider base, more like east Asian women than like African or European women, but that's just a guess.
Body shape is of course under natural selection for efficiency, those that could get food at depth would have advantages not shared by those who only beachcombed.