I had to use a regular hand saw to cut open the coconut. If stranded on an island, how do you open a coconut? Does it explode if you cook it?

Sharp object. My son can open a coconut in about 30 seconds with the edge of a sharp piece of steel like a fence post or the edge of a sharp rock edge by hitting it repeatedly. I would think cooking would build up pressure and explode it not to mention that you'de denature the beneficial vitmins and nutrients with the heat. Have fun with it!
Coconut. Here's a site providing instructions (with pictures) for opening a coconut.. Have fun. http://www.howtoopenacoconut.com/ i suspect the nut might explode if heated quickly. Don't risk injury by trying to do so.