So I recently crewed on a boat that had several "out of town divers" on it, including their instructor. After giving the dive briefing for our night dive the instructor came up to me and told me that he would be jumping in with his group negative. I said something like "WTF are you talking about". He said he had cleared it with the captain and that the captain said to let me know since I was guiding for them... I clearly stated my concerns yet still agreed to guide for them since I probably would not have been welcome on the boat again if I did not... I jumped in first and waited for everyone else before I descended, though some were already half way to the bottom. On my descent I found one diver to be in distress to say the least... He lost his mask on entry and was rapidly sinking to the bottom. I grabbed his inflater and got him neutral. I must have held the power inflater for what it seemed to be 10 seconds.. I always carry a LV spare mask in my BC its small enough to fit in one of my zip pockets. So I gave it to the diver he put it on but had trouble clearing it. I used my other reg to put air in his mask by tilting it back as we normally would and purged the reg to get some air in there. It worked well enough for him to see me which is all I wanted. I was trying to calm him down, I hoped when he could see me he would relax. Finally he snapped out of it and gave me an OK sign, I signaled to him to surface with me. After getting him back on the boat, I went back to find the other divers. I did, they were not aware of what happened nor was his dive buddy or the instructor looking for him. Since I could not see any other issue with dive or its safety at this point we continued the dive. Afterwords the dive buddy asked "Hey what happened to --------? My response was "I guess if your instructor trained you properly you would know". The instructor was standing right next to me, everyone could clearly see the expression on his face, he was pretty pissed off at my statement. His response was something I don't believe should be repeated here. I walked over to the diver I assisted and picked up his weight belt. He had 26lbs on his belt. 16lbs would have been more then enough, he wasn't even wearing a wet suit. He never adjusted his weight from the cold water dives when he was taught. I gave the instructor an earful in front of his student, "your student was severely over-weighted, your negative entry BS put this student and the other freshly certified OW students lives in danger by jumping in the water with no air in their BCD's. This particular student had little or no skill in clearing a mask. (no it wasn't the mask size) He couldn't even stop himself from sinking. To me that clearly shows you are a piss poor instructor, but hey atleast you made sure his air was on before he jumped in. Good job". The captain stopped me at that point. Not much was said on the way back to the dock, I left pretty quickly. I did not want to make the situation worse. The diver never acknowledged what had happened or even said anything for that matter to me.
I'm sure there are details that I'm leaving out. I will answer as asked. Question is what would you have done differently?