Mammoth Cave & Surrounding areas

[cellophane]

I'm planning a trip to Mammoth Cave at the end of July and am trying to plan now for the photography aspect of things. I have a 40D with the 28-135mm kit lens and an 85-200mm(?) telephoto that is pushing 10+ years old.

What I am hoping to find out now are advice on carrying a camera in a canoe and into the cave (i have a lowepro slingbag) and some technique advice on photographing in the cave and along a canoe route. I am also hoping to rent a lens for the trip and am not sure if I would be better served with a fast wider angle lens for cave / river views (such as the 17-85mm or the 16-33mm or even a fisheye for kicks) or a bigger zoom & IS for whatever fauna we may see along the trip.

Would it also be worth picking up a flash for the trip or would the on-camera flash work out ok? I am rather uneducated about how to use a flash and when combined with the various manual settings that I still haven't mastered I'm worried that I would spend too much time dealing with settings and not enough getting the pictures.

Thanks!

p.s. sorry if this would be better served in a gear forum. i felt as it related to specific natural features and landscapes this would be the better location.