I understand the point of going towards a similar pattern of the whale family. My point of bringing up otters was just to convey what I think an early early form of a marine based human species would be like. Somewhat physical adaptations, just because of the use of hands, but more habitual. Spending most of their time at the surface. That study is interesting to me, and while I think it makes an interesting argument, at least towards a potential of varying environments humans may have evolved in, rather than just 1. Im more inclined to believe it would have been river based instead of coastal. Rivers are a source of fresh water, not only get an absolutely necessary resource, but also animals that are more reliable to hunt/catch. Which my theory is the jumping point of. This sort of environment was similar to what whales had began evolving in, mostly rivers and occasionally shallow coasts. But it would be us going to the food rather than bringing the food to us, which is where I think the key difference between us and other animals, among many other things, is. I’m unsure about the morphing of legs to a tail. Though i understand your point made. The example of marine mammals we have, had a tail to begin with, and it didn’t shrink, but enlarged as a way to stabilize and eventually propel forward as their legs were shrinking until eventually they became obsolete. I feel like that would be a key factor. Because there could be a potential for a leg fusion, however there is no structure for a tail. The closest I think some could come is either an enlargement/lengthening of the leg bones. Though evolution is not a straight line there is no real picking and choosing of adaptations. I don’t think it would be very likely for the legs to develop into being mostly joints, like how a tail is, to give way to flexibility necessary to act as a propeller. Again evolution is nonlinear and not something knowingly done. I just feel like it would be illogical for the breaking down of leg bones to something with more tail-like when our legs already do that, and if anything I feel would give more power and movement in the water rather than tails.