Body needs a lot of things that can become poisons if you overdo them. Constant drinking of water (forced or induced by failure of some physiological mechanism

Body needs a lot of things that can become poisons if you overdo them. Constant drinking of water (forced or induced by failure of some physiological mechanism i.e. taste) will eventually lead to liver failure and death by poisoning. IIRC Chinese used this as a kind of torture/execution tehnique.