As for the percentage of the movie that takes place underwater, it’s an answer fans definitely want to hear.
Based on what I gathered on set, it doesn’t sound like there was all that much real water actually used, with actors instead put on wires in chroma key environments, but that’s really a necessity because constantly using tanks would be impractical.
There is no question that Arthur Curry has important connections to the surface world, as his father is human and he was raised as a human child — but when you’re making an Aquaman movie, most of that story needs to take place in areas filled with H2O.