Ahh you knew what you were in for and came appropriately armed.
I was almost bested by a coconut a month ago. I had never opened one myself (in my defence im a mere 25 years old). I thought how tough could it be... I tried my pocket knife (I was trying to gouge a whole in it to get the milk out, i didnt know about the eylets yet, and it said it was "precracked" which was an indent along the middle) then a kitchen knife, tried with a GW, then a drill with a masonary bit, then finally a nail worked; then to crack it i tried a hammer, then a Demo hammer, then the GW again, I thought about getting out my p229, but opted for a try at it with my swamp rat chopper...
That got it done. I have since learned that everybody knows that you drain it through the eyelids on it and that everybody knows they are quite hard...