We could end up with a poorly written character who looks like a wild beast, just to cover it up.
Arthur really comes off as an un-tamed, savage force here. I bet he growls too.
If he truly looks like this, he might be an outcast warrior from the underwater kingdom who had to leave their army due to his brutal and violent ways.
But why isn't he all nobel and sophisticated like the other ones?
Because he's half-human, that's why.
No father from the surface world, then!
Here we change just EVERYTHING
You know that in this scenario, Aquaman would be Wonder Woman's uncle, don't you?
Yeah, away with the Atlantis/Lemuria/whatever it's called stuff, and just let him be a descendent of Kryptonians from thousands of years ago. He has water-based powers just because of evolution, as the Kryptonians went hiding in Polynesia and stayed there forever.
There's no place for a mythological underwater kingdom anyway. It's too fantastical and "meaty" for the DCU. Just simplify everything! Always rely on tech, not magic.