[Gamecock]

Yup.

Your electrolytes get all out of whack and you can die.

It has happened in the military, which is why Drills now push an electrolyte replacement drink during training rather than water. (Not saying recruits don't get water, but this as well)

[Ghost of Philip Marlowe]

It also causes swelling of the brain. This is usually what kills people. This happened a few years ago in a fraternity hazing after a pledge chugged a gallon of water or something.