B1G-
If it were me, I might not do the mapping in the cavern for 2 reasons:
1. Risk of going into a tunnel is great when you are staying below the surface, counting your kicks and concentrating on your compass
2. Those cavern zones are pretty murky. Might be easier to map somewhere w/ >10' vis.
On the other hand, you might welcome the challenge, so of coarse it's up to you!
I appreciate your concern. Phil and I actually did wind up swimming into a side tunnel at one point. Phil was a few feet above me, and he swam into the wall while I kept going. He realized what happened, and grabbed me to stop me from going any further. We were only in about 6 feet.
I wasn't too worried at the time for a couple reasons. First, I was checking the surface with my light a bunch to make sure I had air above me, so I knew I couldn't swim too far in without noticing it. Second, I was keeping the wall within reach on my left side. When I did head into the side passage, I knew how to get out by turning around, and keeping it on my right.
Another precaution you could take to make sure you don't accidently go down an UW passage is to tow your SMB or lift bag. If you start going under a ledge, it's gonna get awfully hard to keep pulling it, so it'll tell you to get out, and its a line to open water.
About the UW mapping, I'd still love to do it, if nothing else because I don't think its been done before. I'm not sure if a compass would give a real accurate reading with all the lead in the mine still, so we would probably have to use surveyors techniques. I would definitely be using tapes or cave line instead of counting kick cycles. With the way I plan on doing it, it should be very unlikely we go anywhere accidently. We would also be measuring everything with lines, so we would always be holding a line leading to somewhere safe. When we do find the passageways leading to overhead, it will nice to know we have them marked for anybody diving through in the future.
Later,
Tom
Tom
