Quote Originally Posted by Papa Bear View Post
First, you are talking about diving in a overhead environment! You should always have a topped off tank and should never dive a tank smaller than your buddy! In Cave Diving that can get both of you killed! When you are in an overhead situation you have to think of your buddy team as one unit. You have to carry enough air to get both of you to safety! It is the rule of thirds! And you are going in a third down to start! If your Caribbean diving in open water I could care less! But if your doing a 63cft in wreck dives you won't be my buddy or I wouldn't let you in the water on my boat! Take a wreck course or a cave course! You can't make more are at 80ft! For Some people a 63cft is a bailout bottle! you can always dive a bigger tank than your buddy but never smaller!
I definitley agree with getting the proper training portion of your post papa. However, in a perfect world everyone would be diving the same tanks, this isn't the case however. When planning ANY dive turn pressures/volumes should be calculated based on the person with the smallest amount of breathing gas and/or the highest sac rate.
I'm not a cave diver..........yet, but I have heard of cave divers re-calculating 3'rds/6'ths and heading back in for a little jaunt in the cave so I'd say these folks are heading in with a less than full gas supply. For any overhead diving, the team should be configured the same with redundant gas supplies, proper training.