I posted simply because I felt this situation after 200+ dives was not for me, sure divemasters are some of the most seasoned divers out their but not immune to accidents. this rather "LARGE DIVER" dawarfed the divemaster and if he wanted to prevent the divemaster from getting air, he could have. What if the divemaster had an emergency?, would he then sprint to another diver and now you have 3 divers on a single tank. I posted because it so confused me, i'm YMCA open water certified and PADI advanced certified and never has an instructor tell me to share air to extend bottom time. Lastly the diver I described actually sat out the second dive and looked visually disturbed.