drinking six liters in three hours has caused the death of a human.

That sounds like a very small amount in three hours.

I had a situation when I was stuck working in a very hot engine room. I went through a gallon in an hour and got Ill afterwards. I still don't know if it was the heat, water or a combination.

Either way, I did learn that if I get in a situation where I'm so hot that the sweat is running, the answer is to cool off, not just slam water.