If you are stranded somewhere on an island, the coconut water may be your only source of hydration, in which case you could survive on it for your hydration needs for as long as water if you are careful, since it is a diuretic.

Can you survive off just coconut water?

Sports nutritionist Nancy Clark, author of Nancy Clark's Sports Nutrition Guidebook, says coconut water won't rehydrate the body unless you can drink plenty of it. If you enjoy the taste and can tolerate large amounts, it could help keep you hydrated.

What single food can you live on?

You'll be eating your own heart, too. However, there is one food that has it all: the one that keeps babies alive. "The only food that provides all the nutrients that humans need is human milk," Hattner said. "Mother's milk is a complete food.