Grant Thompson took a moment from his trip to Hawaii to show how to bust open a coconut without expending more energy than the coconut will provide. There are two parts: getting through the outer husk, and cracking the nut itself.
The first part requires setting the coconut upright and dropping a big rock on the rounded end until it starts to split in a few places, then flipping it over and delivering a coup de grace to the pointy end. After that, you can husk it like corn until you have just the nut.
Once all the fiber is stripped away, look at the end with the "face," and find the ridge that runs behind the two indentations that resemble "eyes." Find a sharp-edged rock, align the ridge of the coconut perpendicular to the edge of the rock, and give it a good hard whack. A clean line should open up allowing the coconut to open right up. Only drink the coconut water if you are stranded on an island, because coconut water tastes like giraffe saliva mixed with suntan lotion.