Photographing Indoors

I'm at a Spanish Water Dog event next week and it's going to be in an indoor swimming pool. How would I be able to take photo's with the usual lighting indoors. Is there any cheap help i.e. something affordable that would help me as unfortunately I don't have a lot of money?

Oh also are there items that you attach to your camera for underwater photography or does anyone know of any that are in a reasonable price range?