This thread is not news to most SB members, but it may help new divers. Despite fully understanding the what to do/not to do to answer the question, I always find it interesting to compare my underwater movements and their effects on my RMV/SAC. I download all my dives from my AI computer, and evaluate my actual RMV/SAC numbers vs what I was doing and feeling underwater. An excellent comparison for me is to look at my volunteer dives at Spring Lake, San Marcos, vs a slow, easy, shallow Caribbean Reef dive. Although the water is colder at Spring Lake, I am equally warm and mentally relaxed in both dive environments. The main difference is how much I am just moving my hands. At Spring Lake, I am almost constantly moving my hands while removing invasive vegetation, or fanning the sand away from the spring's hundreds of water outlets, while on the Caribbean reef, I sometimes think I could fall asleep just watching the reef critters. Being in the .5 -.59 cu/ft/min in @scubadada's air use survey, I certainly am not a gas sipper like many on this board, but when relaxed and barely moving on a pretty reef, my RMV is usually .49 -.53, whereas when moving around a lot at Spring Lake, my RMV has been as high as .69. While I am never surprised at the difference, it is always a good reminder for me to go slow, easy, and stop fidgeting with my stuff. Busy hands waste gas.