Knowing how to open a coconut is one of those things that many people think they possess until they actually do it. That's because they're usually using store-bought coconuts and steak knives. That's when they realize they didn't actually know how to open a coconut.
In the bush, as these videos from P.R.E.P. shows, things are different. The coconuts are greener and contain more layers than the store-bought kind. For survival situations in tropical climates, it's important to know not only how to open a coconut, but which parts are edible.
Once open, the water inside the coconut can hydrate and replenish sore muscles with potassium.
Coconut meat can offer important calories, too. Just don't overdo the meat too much. The flesh can be a double-edged sword. Depending on your body's condition, you may wind up with diarrhea or constipation.
From Livestrong.com:
Bouts of diarrhea lasting more than three days can lead to dehydration and electrolyte imbalance. Diarrhea that lasts more than a week can indicate an underlying serious illness, such as colitis. Contact your doctor about severe abdominal pain accompanied by a fever that occurs with diarrhea. If you're experiencing an acute episode of diarrhea, however, coconut meat or water might help relieve your symptoms.
Moderate consumption of coconut meat is probably the best bet in either situation.