I came across a Hawksbill turtle feeding in the coral (probably after black sponge) and decided to swim into the shallows and cut a piece of a type of sea weed she was eating days earlier and see if she would be interested in the offering. While in the shallower water, I noticed a green sponge which you just don't normally see and sure enough, it was on the back of a crab.
Thinking I could get it to move and show some activity if I proded it with my folded knife, I switched to video and gave it a shot:
Well with the current making it difficult to stay in place and limited time holding my breath, the video approach didn't seem to be worth another attempt so I switched back to still frame and went down again. I was able to coax the crab away from its spot and it flipped over on its back. I held it down for a couple shots and then let it back up.
The next day, 7-18-09 I was at the north end of the reef and noticed some green sponge (which I never see by itself) and sure enough, under it was another sponge crab. This one was a very large one with big claws. I took some shots and then used the folded knife again to coax it out and into some movement.