Thank you for you kind words Yvsa. Cave diving and dry spelunking both have inherent risks. You simply MUST be well trained, be on your A Game for each dive, and never take your safety for granted. And NEVER NEVER NEVER break the rule of thirds. That rule is breathing a third of your gas to go in, a third of your gas to come out, and retain a third of your gas for emergencies. To practice less conservative diving in this environment is asking for trouble. ANd always remember that there is NOTHING so cool, valuable, or expensive as your own butt. Make sure that you remember that and bring it back out each and every time. You can always come back to recover abandoned gear.
Those are some pretty good questions you asked. I can't really give definitive answers to all, but here's what I can say:
Surface support is the team of folks who are in charge of aiding the divers from dry land. In this role, we carry rebreathers, scooters (DPVs), staging bottles, food, etc. to the water where the shallow water support divers take it from there. We also coordinate rescue/emergency operations and plans in the event of a mishap. Fortunately none have happened on my watch.
Shallow water support is the team of divers who transfer gear and run diving errands to a maximum depth of 100 feet.
The deepest I've ever been in a cave has to be (and I don't have my log book in front of me) around 150 feet. Actually it is probably a little less, but that is the ballpark.
As for light reaching the bottom of a cave given the proper water conditions... Wel, technically, as long as you are in a portion of the cave where you can see daylight, you are in the "cavern zone." So technically, no. There is NO sunlight in a cave. All you have is the lighting you bring with you.
As to how far sunlight penetrates in clear water... That was something I had to learn for my class, but never really had any practical application so I promptly forgot the actual figures. What I DO know though, is that different wavelengths of light penetrate farther than others. For example, below 30 feet, red appears green. I remember this because I cut my finger on a rock while diving (I didn't realize it at the time) and needed to write something on my dive slate (underwater note pad). As I grasped the slate, I noticed what appeared to be green algae trapped under my thumb. I shook my hand and regrasped the slate - and lo and behold, the algae was still there. I took a closer look, and came to realize that it was actually blood leaking out from a small slice in my thumb. Actually, it was pretty neat.
And as for the clarity of the water, I've been on dives where the water was so clear, that I literally had the sensation that I was flying. One experience was so beautiful that it brought tears to my eyes. It is a truly remarkable thing to do. I will say, though, that I am not one of those folks who likes diving through tight restrictions (tight spots) and really narrow caves. I like the giant chambers. They are awe inspiring.
I'm sorry you have lost friends to the sport.
