I was certified 32 years ago when was 10 and just recently back in the hobby full force. I have a dive boat question. So now that everyone makes there own dive time on charter trips with their computer. how are people figuring dive times? For ex: if its a 40 foot dive and someone on the boat is diving nitrox or only hang between 25-32 feet, they could stay under greater than 2 hours probably. Is there an unwritten rule on how long people stay under as a courtesy? Or how close you get to max bottom time on your computer? On this trip, I was the last one down since I was with my 10 year old who had a little problem with going down due to clearing ears. We went down about 7 minutes after everyone else. However, when I looked at my computer (diving regular air), I still had 25 minutes left and most divers were doing their safety stop. noticed some were diving nitrox on this 60 foot dive but also came up with regular air divers?!?