On my last dive weekend, I somehow managed to forget to pack the tray and handles for my housing. I had the strobes, and arms, but no way to attach them. (In flaccid defence, I had arrived back in country after midnight and had to be in the car at zero dark thirty the same morning). Of course I discovered this while setting up on site. So there was nothing to do other than improvise.
I was able to jury-rig one strobe to the cold shoe in place of my normal focus light, right above the port with no possibility of adjustment. I am used to the flexibility of shooting with two strobes on multiple arms so was really not sure how to make this work, and sure the backscatter would be terminal.
Here are the best examples from those dives. I was stunned to get clean black backgrounds (except the fire goby which took a fair bit of spot removal) and much more 3D light than I am used to getting. I think when I rigged the strobe to the housing I must have pointed it in just the right way to barely edge-light macro subjects. Conclusion: I normally use too much light and don't think carefully enough about controlling it.
Anyway I'm happy with these shots and will work more at incorporating this lesson even when I remember all the bits and pieces!