Don't know if this is the right forum but my question is about the increase in drag caused by using a pony bottle. I am a recreational diver and use a 30 cu. ft. pony bottle clipped to the front of my B.C.D. to add 37.5% to my air supply. On most of the Carribean Island diving I do they only have Aluminum 80 tanks available. Notwithstanding the usual comments I get about needing to learn to breath better, sip my air, relax more, skip breathe, breath through my nose etc... etc... etc... I was wondering if there was any truth to the divemaster's claim on my last trip. She said that I was probably adding so much drag by using the pony bottle that it negated the additional air from the pony bottle by increasing my air consumption. Anyone know if using a 30 cu. ft pony bottle on a leisurely paced recreational dive would increase air consumption by 38% or more?