It's as deep as you are willing to go! Naturally that can be scary.
We had scoped progression on how deep it goes with key variations occurring along the decent, however as naturally occurs in Game jams, we had to set our goals within reasonable limits, so it is endless.
So in the current state, the limit is only your daring, how deep can you dive and how much gold coins can you grab before succumbing to the chaos of the Perilous Depths.
Thanks for the compliments, we appreciate it very much, exactly the mark we were going for cute and creepy.