Hi Jim Bob,
Photographing in showcaves is generally a pretty difficult task, due to the obvious dark and wet conditions. Also, some showcaves prefer you not to take photos, or at least not to take profesional equipment such as a tripod or external flashes. This being said, if i was going i would probably only take my camera, with a nice flexible zoom, veering towards the wide. Possibly a flash on top, as long as it is quite a way from your lens (or else you'll get misting). An extension cable would be ideal.
As for settings, it depends a lot upon what camera you've got. However, try not to use your flash at all. Showcaves, although dark places, are generally lit up pretty well, with lights in good places, and often with nice coloured filters. Image Stabilizer helps a lot, also resting the camera on the handrails obviously helps. I'd guess you'll be looking at 1/4 sec exposures at least, so maybe have a stiff wiskey before you go to steady your hand!
I'd keep the ISO low as well, or else you'll lose the colour and quality pretty quickly on long exposures like this.
As for getting nice photos, i always find that having people in the shot helps with scale and atmosphere. I've seen hundreds of shots of cave formations and got no idea how big any of them are, making them imediately boring to me! However, i may be looking at it all with a different slant than most!
Pooles Cavern is a great showcave, your bound to get some good shots. Post some up later if you do. Hope this helps!
