The last time I heard about a Namor movie, they were making it more like Aquaman (a surface dweller finds out he's a prince of Atlantis). But that's all wrong. He's supposed to be raised as a prince under the ocean as he comes to hate humanity. That's the whole key to the character. And if you were to do Namor properly, it would be absurdly expensive with huge CGI deep sea environments for much of the movie.