Even if they could have made something happen on screen, the fact is that any sort of fake “underwater” effects would need to be used a lot more often than a Superman flying scene, even if something could work in short bursts, it would never have stood up to consistent use.
While effects technology allowed Superman to fly on TV and in the movies, even that never looked quite right.
Trying to do something similar with Aquaman would likely never have worked.
There’s little argument that there’s truth in these words.