Nah. Been to some of the ones ya walk through (Cave of the Winds, Carlsbad Caverns, etc), and not always the tourist ones like I listed, but never dove in one
Yes (got pulled out to sea by a riptide, luckily I was with my bro, a much stronger swimmer, and he was able to pass me his flippers and we swam diagonally towards the shore eventually reaching land a few miles down the coast where I promptly collapsed on the beach)