This is how you safely open up a coconut, whilst being able to reserve the liquid inside. 

• Firstly set a large bowl on the bench. You''ll need a strong knife here, and you use the back of the knife (the strong flat edge) to tap along the circumference of the coconut.
• Holding the coconut in the your other hand, gradually turn it so that you strongly tap in a line all along the circumference.
• You will eventually hear a hollow crack, then force away the two parts.
• The water will run into bowl and you can strain this after if you're using it.

And there it is, a halved coconut.