Re: Namor the Sub-Mariner
Definitely on board with him propelling himself from the water like a dolphin. I love the artwork where he bolts out of the ocean filled with rage, water splashing everywhere. That could be such an awesome iconic moment on film - especially when he attacks New York and battles the original Human Torch or when he takes down the Germans dropping depth charges over Atlantis.
However, Namor still needs to be able to fly even if it's short distances or at low speeds. It's a defining part of his character and helps distinguish him from Aquaman. The ankle wings are part of his mutation since other Atlanteans don't have them. (Perhaps they'll use the Terrigen Mists to explain it.) It's totally bizarre yes but audiences haven't seen something like that before. Is it implausible that the wings could make him fly? No more implausible than a bumble bee. Just make them move really fast.
It also hearkens back to mythology - maybe you could even embed his story in the legends of the Greeks and Hermes etc. like they did with Thor (jumbled up with legends of Atlantis). That might be a nifty touch. Of course if they did that he'd have to be a lot older than he really is. Maybe there was an ancestor who shared the mutation.