I took it home and using a hatchet got the outside covering off. then used a hammer to break the husk open. I'm glad I did it on the back porch, not in the kitchen because a wave of disgusting nausea-inducing smell proceeded to envelope me. I'd never smelled anything so bad, I gagged, but luckily did not spew.

I had assumed that coconuts are designed to float on open ocean to spread to other islands, so they wouldn't go bad, at least as long as the outer covering was still intact. wrong assumption apparently.