Many years ago, in the Florida Keys, particularly Stock Island at the Jetty of Boog Powell's Marina, the DEA was stacking captured, contraband boats on top of each other till they were 4 deep. Some were sailboats, but most were go fast boats used to smuggle drugs into south Florida. The confiscated boats were eventually hauled out to the gulf side of Key West near the west end of the Northwest Channel, and scuttled into a huge pile. It became an artificial reef, that in just a few years was completely covered with various forms of marine growth. I dove the site about 5 years after it was put in place and the amount of growth was such that it was difficult to determine if there was a boat on the bottom at all. The grouper, snapper, grunt and many other species thrived over that artificial reef. I wonder why Florida no longer does this - the cost was minimal at best, and from what I recall, they had lots of volunteers that helped offset the cost of cleaning up the boats prior to being scuttled.