I am getting cavern certified sometime soon and definitely plan on doing some cave shooting. I am really interested in this thread as well.
The only slaves I know about are the one's on my S2000 but I have no experience using them as slaves.
Question for you Wendy - where in North Florida are you and what dive shops do you recommend for cavern cert?
My home is outside of Branford where the Suwannee and Santa Fe rivers meet. In the immediate area are Peacock Springs, Ginnie Springs, Cow Springs, Little River Springs, and a lot of others. For cave & cavern instruction, I'd recommend Dayo Scuba out of Orlando- they do a lot of cave training. I trained with them and they're now good friends, highly regarded in the community. If scheduling is an issue, check with Jim Wyatt as well. For dive shops- Wayne Kinnard's Amigos Dive Center, Cathy Lesh's Dive Outpost, or Bill Rennaker's Cave Excursions. All offer training options but they're really equipment and gas shops. Jim Wyatt is now running a dive shop in High Springs but I forget the name of it. Further north, around Tallahassee Edd Sorenson's Cave Adventurers is a great place to train and dive with. Also check the NACD website http://www.safecavediving.com/instructors.asp or the National Speleological Society-Cave Diving Section at http://www.nsscds.org/
The YS-250's have slave sensors but I need to "strategically place" all this stuff, hence the need for off-strobe triggers. One cave alternative is to take a strobe and fire it with an open shutter but that's pretty hit or miss. This photo in France was made that way: http://tinyurl.com/8ablrw7 (it's not mine but it made the cover of the NACD journal a while back).
I talked to Becky Kagan and her husband David Schott a few weeks ago at Amigos; they had just won an Emmy for some video they shot in Eagles Nest, a deep Florida cave. They do some stills and according to David, "it's all about the strobes."
I'm just getting into the cave photography angle after a lot of open water photography but the diving alone is very gear intensive- two and three of everything- so adding a camera and a bunch of strobes complicates things enormously. I think to get good "cavescapes" may take a few dives- setup the lighting then return to shoot. Maybe I'm overthinking things, though- there are some very good images done without going to extremes. On the other hand, how Wes Skiles managed an IMAX camera in a cave is beyond me!
Good luck with cavern and hope to see you in cave country!
Wendy