Well obviously any lifeform has water problems. Like any other lifeform, our life depends on remaining within osmotic balance with whatever we drink and eat. T

Well obviously any lifeform has water problems. Like any other lifeform, our life depends on remaining within osmotic balance with whatever we drink and eat. That said, the amount of ways your body adapts to osmotic balance problems is in the dozens, so poisoning your body with water, while possible, is hard to the tune of it requires something like drinking 20 liters of water in less than an hour. I mean, it seems to be possible but I cannot imagine succeeding at that even if I'm trying. That's 2 full buckets (and that's just LD50, as in, if you're >70kg it's more than that). There is an exception: purified water. You cannot drink mineral-poor* or distillated water safely in even small quantities. Why not ? Because that will locally, suddenly and very strongly disrupt the osmotic balance in what you bring it into contact with. It probably not kill you (not without repeated application), but it may cause serious issues in your mouth, throat and stomach. It should also not be used to make coffee or tea and drunk, that merely lessens the effect it doesn't stop it. * mineral-poor water is something used in chemical and medical laboratories