A feast of fluorescence
Night diving with fluorescent lights opens up an ethereal world and is a bit like a treasure hunt as you never know what's going to light up in interesting patterns as you shine your blue torch over the reef. As I passed this brightly fluorescing Acropora coral, I noticed something swaying on top of it which was also fluroescing. To my astonishment this was a Decorator Crab which had covered its body in anemones for protection from predators. These anemones also fluoresce brightly under blue light, and between the anemones and the coral these two fluorescing sources of light then reflected off the crab's carapace to illuminate the (non-fluorescent) crab. I had an opportunity for 2 shots before this crab scuttled away to a darker and more protected part of the reef, but fortunately that was enough to get this shot.
This was shot with a blue video light for spotting, 2x Retra Pro X strobes with excitation filters to produce most of the blue light, and a yellow filter to block any of this blue light from returning to the camera lens so that any light captured by the sensor is due to fluorescence.