RickI
Contributor
True, most of the negatives applied at greater depth. Then again, I never wore the backup gear for shallower dives to 70 ft.. Doing a free ascent after breathing compressed air from 90 ft. would be problematical. I think I may have done one while scuba diving, stupidly but with continuous exhalations as a young teen from around 60 ft., without negative effects that time. I wouldn't recommend it, much less stretching it to 90 ft.. Ideally, you would have enough air to make a controlled ascent and never have to go into free ascent mode. Still, once you take a breath of compressed air on a breathhold dive, you're committed to that slow ascent and exhaling on the way up. Focusing on conservative bottom times and maintaining capacity reserves while free diving are key.
For a good freediver and good scuba diver switching over to scuba at 60-90 ft would seem to be trivial, but we all make our estimates of risk and reward and then bet our lives on it..