Just one suggestion on checking air with a buddy....especially the first couple times you check, you should get a "number" (ie 1500 psi or 100 bar) rather than an "ok." That way you should have a fair idea of how much air the other diver has left based on comparing it with your own consumption. Unless something unusual happens during the dive which would cause that diver's consumption to really pick up, it will stay reasonably constant. As a guide, I have to do that all the time...sometimes have quite a few divers to monitor, so within the first 10 minutes I check everyone's air, which gives me an idea of the "heavy breathers" who I can watch more closely, determine the dive time, etc. (We'll normally have a depth & time planned in advance, both of them subject to "downsizing" as conditions/divers' skills dictate. I won't do a 40m/130' dive when I'd "planned" an 18m/60' dive, but I WILL do it the other way around, if I decided for whatever reason, once we descend, that the more challenging dive wouldn't be safe on that day.) Oh, and it's also a good idea to know (about) how bar & psi equate. 1 bar = about 15 psi, so (for a 3000 psi tank) 200 bar is full, 100 is half, 50 bar is 1/4. Hope some of that info is useful to you. If a buddy gives you no info other than "air is ok" prior to "out of air" it (obviously) puts both of you in a difficult situation; glad you handled it well from that point on! (but do your best to avoid it "getting" to that point, ha ha.)
.... Yes, I know planning is prudent but ....
