We've all been there...gas limits BT for almost everyone at first, but it DOES get better with experience....Here's my quick thoughts, which mirror others, but with a few adds/tweaks:
1) RELAX AND DON'T THINK SO MUCH: If you focus on how much gas you're using, you'll use more...focus on other stuff on the dive and you'll naturally relax...IMHO, novice divers tense up a lot during a dive, and this creates a viscious cycle...they have a lot of air in lungs, which is +B, which they offset by over-weighting, which then leads to more exertion underwater, etcs...and all of this activity leads a lot of people to just start thinking about it all WAY too much...all leading to increased gas consumption...Diving for most folks starts out as an adrenaline rush activity, and ends up being a zen-like activity (I still remember the first time I surfaced after a 50+ min dive and was worried b/c there was a period of 5-10 mins I just completely felt at peace...I was afraid I was narc'd or something...When I asked what was wrong with me, the DM laughed and said, "DUDE....That's why we dive!")...This is why people say to get more dives in...With experience comes the natural transition from adrenaline rush feelings (which is natural when doing a new activity in which one often first feels like "God really never intended me to be here...I really hope my equipment works!") to zen-rush (when the voices in your head just "disappear" and the real-world fades away!)...And Zen consumes less air, by FAR!
2) PACE YOURSELF WITH A BUDDY OR DM: Find somebody in your dive group that consumes a "normal" amount of air...for a few cycles, and without telling them (don't make them think about their breathing) deliberately breathe in synch with them...You'll get a sense pretty quickly where your breathing pace is relative to others and how it differs....I'm sure someone will point out inherent dangers in doing this too much, but it can be a helpful tool in both diagnosing whether lung volume or breathing rate is driving your consumption...and it is most likely rate, probably due to inexperience and what I think of as "adrenaline tightness" rather than zen calmness....I do something like this type of pacing when I need to get my young daughter to sleep when she's too wound up to get herself to sleep...I place my arm over her body, which gives comfort and slightly increases the energy required to breathe rapidly, and I just breathe slowly...She very naturally begins to pace her breathing to synch with mine, and she calms down and goes to sleep...You obviously don't want to fall asleep, but pacing to somebody else's breathing inthe water will tell you a lot and help you calm down naturally...if done in moderation...Don't force yourself to breathe like the DM the entire dive, or you'll be violating rule #1 and be thinking too much!
3) DON'T SWIM SO MUCH/LOWER YOUR EXERTION LEVEL: I'm shocked at how new divers always want to cover so much real estate while they're down, hoping a shark is just around the next bend, I suppose...and they end up missing good stuff...You'll actually see more if you swim less...and you'll reduce gas consumption too...not only b/c you'll be exerting less, but b/c you will focus on other stuff and zen-out naturally...When you start to get more comfortable, you'll also naturally want to shed more weight, which will actually help with your BControl, which will get you more horizontal, which will help your gas consumption...and you'll be in a virtuous cycle...and before you know it, you'll be wanting Nitrox so you can extend bottom times!
4) GET A BIGGER TANK: If you stop spending the entire dive worrying about how to get more BT, you'll consume less...crazy, I know, but true...Reminds me of my paraplegic Father-in-Law who was in a wheelchair and needed a Service Dog to help for those awkward times when he dropped his keys and couldn't get them for himself without asking help from complete strangers...When he got a dog, he never dropped his keys again!
HTH!
