He was quite a bit more physically fit and obviously he was an adult (and a former Navy SEAL) and I was a teenager, so yes he had quite the physiological edge o

He was quite a bit more physically fit and obviously he was an adult (and a former Navy SEAL) and I was a teenager, so yes he had quite the physiological edge on me. However, part of what he taught us was that when diving, with our without SCUBA gear, one shouldn't anywhere near approach the limit of one's aerobic capabilities, for precisely the reason of conserving one's air supply (and, honestly to focus on the experience of the dive and the amazing ecosystem around you). I got much better at reducing my use of air by the time I got my open water cert, but I still never got anywhere near to how little he used.