Seeing as I've put in on Twitter I may as well post it here. I don't suppose you're really meant to do this with sharks either - though better than putting them in soup - and I've had twinges of conscience ever since, though these ones were used to public attention. It was taken at Shark Ray Alley in Belize several years ago, in 2004 I think.
I also went diving on the same trip with about 8 or 9 nurse sharks, maybe 8-10 footers. The dive master had a can of guts and entrails (chub I think it's called) and was letting it stream out behind us so that the sharks followed. It was a stunning experience, and one of the reasons I'm so keen on shark conservation now.