I agree with Wally. My first dive in my LP85's wasn't a very smooth one. The buddies I was with were newly minted cave divers. They knew I had 50+ dives in drysuit, but 0 in doubles, but thought it shouldn't be a big deal. The dive plan was to go to abut 100ft & skim over the bottom, up an old haul road of the quarry, BIG MISTAKE. Not knowing the negative characteristics of those tanks, I agreed (I had dove that path many times in singles). When we went to descend, I foolishly released all the air in my wing. I almost immediately found myself in an uncontrolled descent. Also, having only dove singles before, I was trying to descend feet first, instead of in a sky diver's position, so had the tanks trying to pull me over backwards. All that task loading was a bit too much for me. I really didn't have time to equalize my ears, I was really lucky they pretty much equalized themselves. Long story short, I got myself stopped at 95ft. By that time I was in a state of near panic,.... completely stressed. As my buddies caught up with me, I decided to abort the dive & began my ascent. My buddies stayed right there with me & helped me along back to the surface. Once there, I decided to sit out for a while & collect myself. My buddies went on with their planned dive. After a few hours, I found another buddy who was interested in shallow diving. I did another 30 dives in those doubles before even thinking about going deep. I got familiar with those tanks during that time. At that time there was a very good OW instructor who knew of what had happened to me & helped to guide me back to the deep in the doubles. Since then I have been improving & learning more about them. After a year, I now have control of them, instead of the opposite. As Wally stated, start shallow, go with someone with some experience, take your time to get familiar with them.