I spent 10 minutes banging a wooden spoon on a standard kitchen knife trying to open a coconut. I give up after the wooden spoon disintegrates, the coconut still closed.
My wife comes into the kitchen and swings the same knife at the coconut a few times. Less than a 30 seconds later, we have access to coconut water.
I grew up watching my mum crack open coconuts all the time though I've only done it myself a couple of times. I think you have to do it perpendicular to the seam. Whereabouts are you getting fresh coconuts? Are they any good? I've wanted to have a go at getting some but for grating the flesh, not for water.
We've gotten it from a few vendors over the months, like from Queen Vic market, Footscray, and most recently yesterday in Springvale Central.
My wife otherwise thinks they're all not fresh - it lacks the taste of when the young coconut is opened freshly chopped down from the tree. I thought it's so sweet it's almost artificial.
In my wife's home town home we have a rather large heavy knife. A few well placed hits is all it takes to get the water.