I am looking at some old world goose neck lamps. Not the lamp but the bendy metal part. I have not found one that could resist sea water. I think the new "metal" Gorilla-pod could be hacked and butchered into video light arms. If I found one that works as well then I will let you know.
I would agree the 15mm Zeiss is a fantastic wide angle lens.
I recently just came back from a dive trip using the RS 13mm with an adapter for the Dragon housing. Full mechanical control for focus and aperture. The 13 mm RS is now my new favorite lens. Surprisingly it is not as "fisheye" as one would expect. I think on the S35 sensor (approx. 1.6 crop) its like a 20mm.
Some pictures soon when I could grab a hour or two....
Yes. You will need less angle of beam in certain situations. Beam should be even in either spot, medium beam or wide beam. To do so correctly in a powerful light would need some sort of lens/ diffuser.
One thing to note is that better powerful light heads do not use array of power LEDs that is spread out in the light because that would produce multiple shadows.