So I'm having a problem where I use my air to fast. I'm a novice diver and maybe done about 10 or so dives in quarries/lakes.
Every time a dive is over I have like 300 PSI or so and my dive buddies (usually different) have almost 1100+.
For instance today I went out to a lake, I was using a Steel 120 tank and my buddy was using a Aluminum 80.
When the dive was over I had 120 PSI left and she had over 1000 left. I'd say this dive was a good 35-40 minutes at around 15-20 feet.
Any suggestions? I do have a mild case of Asthma and I due tend to use my inhaler before I dive just in case.
I'm not overweight, (5'9 155 pounds) though I'm not really in shape.
Classic case of "new diver's lament" ... most of us go through the same cycle you are. Don't worry about it.
When I was new, my buddies would tease me that they could see the sides of my tank cavitating when I breathed. They'd come back with 1,700+ psi and I'd be down well into the red zone. I didn't think there was any hope.
There was. Here's what I learned, and how I made it get better ...
1.
Make sure you're weighted properly. Most new divers carry too much weight because they think they need it to get down. In reality, they don't ... they just haven't learned how to descend properly yet. There's a few good threads on ScubaBoard talking about descent techniques. Go find them and digest what they have to say. The problem with carrying too much weight is that it causes you to blow a lot of air through your BCD trying to get neutral. And because there's so much air in your BCD to compensate for all that weight, every little change in depth forces you to either blow some air out or jet some air into the BCD. Wastes a lot of gas doing that.
2.
Swim horizontally. New divers tend to swim diagonally ... especially the overweighted ones. Problem with swimming that way is that you have to push a lot more water out of the way to get where you're going. And because what you're basically doing is kicking yourself up a bit, then letting gravity take you back down a bit, you're not only working harder, you're going farther than your buddies ... you're just "wasting" a lot of that distance going up and down. The harder you work, the more air you'll use getting there. Work on that trim ... water's really heavy stuff to move through, and the less you have to push out of your way the less exertion you'll use to get there.
3.
Don't swim with your hands. Most new divers wave their arms around trying to "right" themselves ... when in fact, that just makes it harder. Put away those "special fins" ... you don't need them. The only thing you should be using your hands for is equalizing your air spaces (nose and BCD). Otherwise, tuck your hands into your BCD harness, or clasp them together in front of you, so you don't unconsciously learn the bad habit of waving them around. Using your hands does two bad things ... it forces you to move more water (like swimming diagonally) and it throws your balance all out of whack. In scuba diving, your fins are your motor ... learn to control your movement with your feet, and keep your hands in close to your body.
4.
Slow down. Most new divers are like baby harbor seals ... they're flitting about trying to see everything. Think about it ... how much harder would you be breathing if you went everywhere on land by running rather than walking? Same holds true underwater. Slow down ... you'll breathe less hard, and chances are you'll suddenly start noticing a lot more cool stuff ... speedsters usually miss some of the coolest stuff there is to see down there.
And last ... but certainly not least ...
5.
Dive often. We improve by doing .. and that's just as true in diving as anything else. If you want to get good at it, you gotta get out there and log some bottom time. Get out every chance you get. Take at least a few minutes every dive to practice a skill. A huge aspect of diving is mental ... and when you're new, your brain needs some time to "rewire" for the new environment. As you get more mentally comfortable, you will also get more physically relaxed ... and the key to good air consumption is relaxing.
That should be enough to get your started. My OW instructor told me to give it 50 dives to start feeling really comfortable in the water. I found that to be a reasonable rule of thumb. So relax and have fun ... and your air consumption woes will take care of themselves ...
... Bob (Grateful Diver)
