I am back from my trip.
I used the S&S strobes and they worked great, but I am going to use video lights next year. Much to my surprise, they were way more power than I need. Unfortunately, the water was a bit cloudier than I remembered, so I had to stay within about 15' from the surface I was shooting. That was my original plan, and would have been fine, except that the topography of the bottom of the cave was so complex that staying consistently 15' above the floor meant that I was hitting walls, i.e., there are boulders that are 20-30' tall, so I had to stop and go up 20' and carry on. I tried this, but it wasn't working. SO, next year I am going to use video lights instead, held by two or three divers down around 15' above the floor to illuminate it, and I am going to be up around 30' from the floor taking the pictures. I will be zoomed in and probably have to crop the images, but that will solve my backscatter problem. I need to sell the strobes now, and hopefully get the lights donated or loaned to me next summer.
Edited by Aotus, 23 August 2018 - 05:06 PM.