I set up around the half way mark with an 85mm f1.4 lens.
All these were shot with a Nikon V1 in a pleasantly inexpensive case. (£75.00) using a 10mm lens which is a 27mm equivalent.
I also used a couple of Green Force LED video heads for lighting. Not an inexpensive option including a multi headed umbilical plus power pack. Despite all these shots being at snorkel depth extra light is essential for any realistic chance of a decent colour balance. I could have used flash but the V1 is a pain in the 4rse by not having any conventional flash interfaces. But as I was also shooting video with this camera and a GoPro H3 (black) the video lights were the best choice.
Previously I’ve used Nikon DSLR cameras, 20mm and 85mm lenses in a EwaMarine case plus a D800 flash.
Comparing video output from the GoPro vs. the V1, the V1 wins every time. The only thing going for the GoPro is the wide angle of view it can provide, but usability and battery life are dire. I won’t bother with it again, purchased a cheap underwater ‘point n shoot’ which I’ll try out for video.