I can tell it was an awesome experience for you, I totally understand the fear of having a panic attack especially with things you haven't tried before and one that could be disastrous at any slightest mistake

I was watching a documentary the other day where it was said that at such deep level that one could take in Nitrogen that could be disastrous and kill the person( don't know how true that is)

it is just like skydiving, all these are risky ventures and at same time a worthwhile experience if you can summon the courage to experience it.

Amazing views I must say that is beneath the sea, our world is so big, it all boils down to how much you can see.. I salute your courage..