David Doubilet: So every photographer has to supplement light.  The light that falls down is the backdrop, dramatic shafts of light from the surface.  And to that you add electronic flash, almost as if you’re swimming around with a studio.  It takes that kind of approach.  You are, in essence, trying to catch these creatures, and you have in your hand an underwater camera.  We use these cameras called SEACAMs. They’re big underwater housings with large domes and two flashes that come out to here, sometimes three or four. You look a little bit like a spider crab, a giant spider crab, and you position these lights as you’re moving, as you’re swimming. So it’s basically being a studio photographer, running through someplace on land, running through a field and trying to catch that moment — that decisive moment.