That's correct, the deepest part was 15m (50feet) and I was not pro yet. When I said that I was holding his dump valve all the time it is to say that I was more looking at him and stay close to him in case something wrong happens, nothing else, and I guess that can be quick. He was just certified OW and not fully comfortable so I pay more attention than with my favorite buddy that have roughly my level.
For dumpsterDiver: So if shallow is about 10m (30 feet), we were shallow and I wouldn't go deeper in this situation (our two previous dives was a little bit shallower, 8m that's 26 feet). We were close to shore, our beach was just a bit farther than the site but it was possible to reach the shore near the wreck if needed. I was not waiting the local guide to turn the dive, otherwise I didn't care of my buddy's SPG and never decided to turn the dive at 80 bar for him taking into account the way back. More generally, due to the level of the people that was in our group, the basics of that dive was to me pretty simple even with beginners. Maybe my mistake but what to do when it is part of the training you have to do for the divemaster level?
Anyway, that's great to share this with you and read your feedback. There is a lot to learn from each situation and specially when nobody was hurt.