Yesterday for the first time, other than in a course, I dropped my weights. During an afternoon dive my BC decided it no longer wanted to hold any air at about 55 ft. I started the dive off a boat in Akumal. One DM, a nice couple from the mid west, a local lady who was on her 20th dive and couple from Spain who got cert'ed year ago and hadn't dove since. In the boat I noticed the Spanish couple were having trouble putting on their masks and fins and just in general looked confused. The water was choppy, I say 8-10 ft. Once we all hit the water and started our decent I noticed the local lady was having issues, couldn't seem to descend. So at 25ft I went back up and helped her down. Once she got to about 30-35 ft she was fine. At around 55 ft I noticed I was having problems with bouncy. I'd put a little air in my BC and in within a couple seconds I find myself sinking again. I rolled on my back, put some air in the BC and immediately saw bubbles headed to the surface. A little trouble shooting...