Of course, to a certain extent, in order to work, Aquaman had to have some really impressive visuals. Large portions of the film take place in an underwater city. This meant the movie had to create not only the mythical city of Atlantis but make it look like people were existing there underwater, and had been for centuries. To a certain extent, the visuals would make or break the movie. If the underwater sequences didn’t work then the rest of the movie sort of falls apart.
Article source: https://www.cinemablend.com/news/2463727/shazams-director-has-screened-aquaman-heres-what-he-thinks