I think the whole contest idea was completely idiotic. People can die from drinking too much water, and the contest organizers knew that. It is not clear if the people participating in the contest were told that, and whether the woman knew it, or whether participants had to sign a release form, never mind if there was a physician there to monitor the participants.

http://www.wisegeek.com/what-is-water-poisoning.htm is a good basic guide to what water poisoning is.

It was a stupid, stupid, cruel and dangerous idea.