How quick does this urn break down and release it's contents? People snorkels all along the cliffs, and if someone spots it they will investigate. You don't want someone bringing it up, showing it around and spilling it at the local bar. A little further out the lobster and conch fishermen may spot it. I would hire one of the local boat operators to take you out a ways. I am never surprised to find so many caring people there who want to help.