We've night snorkeled a few times in Bonaire, and it was a really different experience, almost eery, but strangely beautiful. A full moon might help things. I might suggest a spot with at least a few feet of depth/clearance, as you can't see to avoid any near surface obstacles. A headlight or a flashlight should give you a good amount of light to see specific things, but as to photos, no experience. I might think a flash would be sufficient for objects up to a few feet away.