Aquarium and sharks....what lens to use?

I will have an opportunity to dive in a large aquarium with decent sized sharks that come VERY close to divers and bump them out of the way at times...... in addition, there are many types of rays, turtles, Eels, groupers, jacks, etc. I primarily want to get really good shots of the sharks since they won't be shy and traveling slowly. Any advice for shooting under such conditions? I was thinking of using the Tokina 10-17 Fisheye. However, I also have a Sigma 18-50 F2.8 HSM Macro. Would I be right in deciding on the Tokina?

To give you an idea of conditions, subject size and proximity, I have attached photos from the same dive I did last year.... Photos were taken by spectators from the "Dry" side. Advice would be appreciated. I have never used my 10-17 UW, hence the questions.....judging from the Tokina thread though, it seems like the right one to use...

Notice how the shark went straight at me and pretty much bumped me out of the way to squeeze between me and the glass....he was moving real slow too...

what aquarium are you diving at? I volunteer at Georgia Aquarium and we're not allowed to take our cameras. I have dove in Maui and they let us take our camera and I also dove in the aquarium in Bangkok but didn't have my camera. I don't know what lenses you have but I would take a WA. With my camera, I can change lenses uw so I would use my fish eye most of the time. Hope that helps. Scott

Thanks Scott...

The aquarium is Aquaria in KLCC (Kuala Lumpur, Malaysia). Last I heard, they allow cameras. However, I do not know if they will allow it during the feeding session I am hoping to join....

The Tok 2.8 10-17 would be a great lens for an aquarium. Super close focus. Quick focus. And, if the "fish eye" effect is too much for you, use the 17 end. The curvature isn't as dramatic as the wide end.

The Tokina will be fine, some aquarium however don't allow strobes so check first.