Equipment for Wreck Diving Back Lighting

[c-dog]

Any suggestions for what kind of light or slave strobe to use to add light into the background of my wreck diving shots? I have a DSLR with strobes but want to have light coming out of the wreck through a porthole or behind the propeller for example. I have seen this done many times but do not know if these are just large dive lights or slave strobes positioned in the wreck. Any advice on what equipment to try to creat this backlighting effect? Thanks

 

[elbicho]

A dive light with a weighted/magnetic base to keep it in place?
Needs to be waterproof.