I'm lucky - I dive with the world's most disciplined buddies. :-)
For reasons of cave conservation though I wouldn't like to consider a cable option. I can't stand scarred cave floors.
You need a bigger tunnel :-) Long cables are better than tripods from a conservation perspective. You could consider laying one along the line during a setup dive and coming back to take the photo later.
The options I outlined require some DIY as they're not commercially available. The other option is to throw a lot of money at the problem - a few 10,000 lumen heads would give you enough power for reasonable pictures dependent on cave size and colour.
- Alison Perkins likes this