My cat won't stop dumping her water bowl and playing in the toilet?

I have a young cat, about 10 months old. At first she started playing in the toilet... just playing. Then she started to dump her water bowl. So I tried putting less water in the bowl, and that didn't work. I tried putting a towel under it because I thought she liked how it shined on the linoleum, but that didn't work. So right now I have a small amount of water in a really big cooking pot. She can get her head in, but can't spill it. So now she keeps getting into the bathroom and playing in the toilet. Does she just love water or is there some medical problem here? I try to keep the bathroom door shut and close the lid, but sometimes we forget... what's wrong with her? I'm sick of cleaning up water. I have another cat so I can't just take away the water and give it at certain times.