Further information (as I have heard it - and seen it)
I heard that the wreck was pretty dull for the first few years that it was down, but sometime in the spring of 2003 a huge school of bait fish (I have heard differing species mentioned) moved in to the wreck. That of course brought lots of other fish.
When I was there in June 2003 there were millions of bait fish in a giant bait-ball hanging out in a couple places within the wreck. The bait ball was amazing. They would part for a diver, then close back in around him. The entire mass would react as one to any movements. It was like bing inside a sphere of living mercury. You couldn't see a diver 8 feet away when the school closed back in around both of you.
There was a good sized Nassau grouper hanging around outside, and a three foot long grouper of unknown species hanging in a corner inside, just waiting for his chances. He tolerated divers coming past, and he used us as a distraction to get a mouthful of bait fish at a side opening.
There were also a a bunch of Glassy Sweepers hanging around on a lower (darker) deck area.
There was a fair sized barracuda hanging near the wreck, but he retreated whenever divers approached the wreck, and returned when we surfaced.
There was a juvenile drum with the long flowing fins hanging around at the top of the superstructure, and arrow crabs everywhere. There was a pair of French Angelfish that owned an upper walkway on the port side of the ship, plus a few other species cruising around. I have a couple decent pictures from my cheapie camera, but they are home.
I loved the C-53 Wreck when I was in Cozumel. I dove it twice, and I will definitely hit it again when I go back (hopefully in May or June).
FWIW
Wristshot