Ever seen a new DM with all the cards panic trying to do a simple weight belt swap? Watched one drop the whole thing because their hands were shaking. All the book learning in the world doesn't prepare you for the real weird stuff that happens down there.
Man, that's so real. What do you think is the biggest gap between the cert class and actually being on a boat? Seems like we focus on big emergencies but the simple stuff under pressure is what gets people.
Honestly the amount of people who get down there and realize they never actually turned their air on. All that training and you forget the one thing that, you know, lets you breathe.