I like the water ape theory. ie we had a period of time in our history where we spent a lot of time in low lying water that encouraged us to stand upright. There's a few things which point in this direction. iirc we're the only primate which can control its breath; good for swimming under water. Our fingers wrinkle when we spend time in water; good for picking things up in water. And we lost our hair; hair may have g…
It's fun to think of the ramifications though. Are/can we look for human fossils in the right places? How much of our history is potentially under water and not African caves. Did it help spur fire usage so that we could safely eat fish? Did it influence the out of Africa migration which was mostly coastal (we got to Australia before Europe)?
It probably didn't affect our evolution much but I suspect a lot more of our pre-history was spent at least on the shallow ocean than we have evidence for.