I think the message is do not drastically change your fluid intake at anytime. Below is a paste from a "competition" a radio station ran in Sacramento CA in 2007 which led to the death of women from water intoxication. This text comes from Wikipedia.
Allan.
Death of a contestant in KDND radio contest
On January 12, 2007, a listener named Jennifer Strange, 28, died of water intoxication hours after taking part in the "Hold Your Wee for a Wii" contest in which KDND promised a Wii video game system for the winner. At the time, the Nintendo console was a very popular and sought-after item, but also nearly impossible to find in North America.[3][4] In the competition, contestants were asked to drink as much water as they could without urinating. The contestant able to hold the most water would be named the winner.
According to contest participants, seventeen to twenty contestants took part in the competition in a room at KDND's studios. The contest was broadcast during the station's Morning Rave program and began around 6:15 a.m. as contestants were each handed 240ml (8oz) water bottles to drink at 15-minute intervals. Contestants also said that as the contest progressed, they were given increasingly large quantities of water to drink. Some later remarked on the physical discomfort they suffered during and following the event.
The Sacramento Bee released audio clips from the morning show indicating that the disc jockeys were aware of the death of Matthew Carrington by water intoxication.[5] At one point, a caller contacted the station and informed the DJs that the contest could be dangerous and potentially fatal.[6] The DJs responded by saying, "We're aware of that," and joked that the contestants had signed releases and couldn't file a lawsuit. However, according to a contestant, the waivers addressed only publicity issues and made no mention of health or safety concerns. The DJs also joked about Strange's distended belly, joking that she looked three months pregnant.[7]
After the contest, Strange spoke to a co-worker by telephone, indicating she was on her way home and in extreme pain, suffering from what appeared to be an intense headache. The co-worker contacted Strange's mother, who went to her home an hour later to find her daughter dead.[8][9][10]