High air consumption is common in newer divers. Some basic tips that may help ...
1. Do a weight check ... make sure he's not using more than he needs. Lots of new divers tend to overweight ... usually because they haven't been taught how to descend properly and think they need all that extra weight just to get down. If you need more info on doing a proper weight check, ask. If you need more info on doing a proper descent, ask.
2. Avoid poor trim and hand sculling. Both tend to force you to move more water than necessary, and water's heavy stuff. It takes effort to move it outta the way, and effort makes you breathe harder. Keep your body as close to horizontal as possible when moving through the water ... and one way to teach yourself not to scull with your hands is to keep them clasped together in close to your torso.
3. Slow down ... most newer divers tend to zip around trying to see everything. But it's like the difference between walking and running ... running makes you breathe harder. Take it slow ... not only will you improve your air consumption, you'll see more.
4. Dive as often as you can ... like most things, the more you do it the better you get at it. And with better technique comes better air consumption.
... Bob (Grateful Diver)