Sight. I don't even know how/where to start.
First of all, the visuals. One of the most fake visuals of current superhero films. Yes, tons of visual effects, but everything looks extremely fake. And not only the CGI, but all the costumes look very costumeish. Even the weapons look very plastic and toy-like.
The underwater scenes. Everything lacks weight... Nothing, absolutely nothing feels like it is underwater. Nothing moves of behave like being underwater.
The soundtrack. What soundtrack? Completely unmemorable. Can you remember a single tune? A few notes? No. No one does, because it is one of the most boring and unmemorable soundtracks ever created.
And the chemistry between Arthur and Mera? Zero. Nada.
The jokes... Oh, my. The jokes/humor feels very tacked on, trying to be similar to Marvel. Arthur sometimes feel like it is trying to emulate Thor's humor, but fails spectacularly.
And what was even the point to include Black Manta? Completely wasted character.
The film is complete garbage. I wasted two hours of my life watching this film.