If Aquaman showed up on the Flash, would you be okay with him being one of the "metas" created by the incident at STAR Labs (awful close to STARK there), or would you be more comfortable seeing him as the King of Atlantis, half human, half Atlantean/Merman/whatever-the-hell-he-is?
I think it all depends on how well it’s executed.
But that said, it wouldn’t be my first instinct to try to make him a byproduct of that same accident.