A cubit is roughly 18" in.<quoted text>
So the flood was 15 cubits (whatever a cubit is) ABOVE the highest mountains.
So, 30' ft.
This is something I've noticed with Ar Ar, and other theists. They'll make these grand claims or bare assertions, then when it appears there is going to be an answer given that necessitates an acknowledgment of a term or admission of being mistaken, they will disappear for a few days, return, never mention it again if possible, and ideally move away from the ridiculous claim they made.
Ar Ar does it consistently.