The freak incident occurred when the mother-of-two chugged multiple bottles of water in a short space of time.
36-year-old Ashley Summers from Monticello, Indiana had been enjoying a boat ride on Independence Day during particularly warm weather when the incident happened.
Having been extremely thirsty, she consumed four bottles of water within the space of 20 minutes.
Upon returning home, she complained of a sore head, passed out and then never woke up.
According to doctors, Summers had suffered from water intoxication – a rare condition that can occur when someone drinks so much water that it throws off the body’s electrolyte balance.
This, in turn, causes sodium levels to drop, resulting in lethal swelling of the brain.
“It pinched off her blood vessels like a kink in a hose and just stopped the blood flow to the brain,” said her brother, Devon Miller. “It was a big shock to us all. I was just like, this is a thing?”