Look up "hyponatremia" on Wikipedia:

http://en.wikipedia.org/wiki/Hyponatremia#Notable_cases

Notable cases

Matthew Carrington, a student at California State University in Chico, California, died of hyponatremia in February 2005 during a fraternity hazing ritual [1].

James McBride, a police officer with the Metropolitan Police Department of the District of Columbia, died of hyponatremia on August 10, 2005. Officer McBride had been participating in a strenuous bicycle patrol training course. During a 12-mile (19 km) training ride on the second day of the course, Officer McBride drank as much as three gallons (11 liters) of water[2].

Leah Betts[4] died on the 16th of November 1995 after taking an ecstasy tablet at her 18th birthday party and subsequently drinking too much water; the case received mass media coverage throughout the United Kingdom, which focused on the dangers of ecstasy.

In January 2007 Jennifer Strange, a woman in Sacramento, California, died following a water-drinking contest sponsored by a local radio station, Sacramento-based KDND-FM.[3]. The fact that the contest was called, "Hold your wee for a Wii" has led some to believe that not urinating is related to hyponatremia. This is untrue; this type of water intoxication is caused by excessive and rapid consumption of (sodium-free) water.

After completing the 2007 London Marathon, 22-year-old David Rogers collapsed and later died as a result of hyponatremia.[4]
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As you say, *everything" is lethal in sufficient quantities.
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"The mind is not a vessel to be filled but a fire to be kindled."
-Plutarch