I experienced "water poisoning" once when I went on a walk through the Olgas near Ayres Rock. It was very hot and I drank lots of water, but because my
body was flushing out the salt through perspiration, I got myself into some difficulties. I thought I was dehydrated, so just kept drinking more and I was walking and perspiring.
But once I had some food/ salt, I felt alot better.
I think it has to be fairly extreme conditions before you get into this state, and for me it corrected fairly quickly, although I didn't/ couldn't pee for around 5 hours after the experience.
HL