Hey all, Just looking for some ideas on sealing up the end of a coconut shell so it will retain water.

I tried to make a cork fill the hole which worked fine until I placed it into the substrate. The pressure of the substrate seemed to cause the shell to leak.
My next attempt was to use some sportsman goop to seal from the outside but it doesn't stick to the shell exterior.

Any ideas? It looks awesome in the viv but if don;t hold water its not going to make a good place for the Whites to soak.

Thanks for any replies.