You could really wallop someone! Haha, Catalina is a mountain top sticking up out of the ocean and there's lots of rock to spare. There's really only one small town and the rest is mostly only accessible by boat. It's really pretty and a hugely popular place for people with boats to visit. I'm sure it was way cheaper for them to load the rocks on huge barges and then dump them off where they wanted them here in the water. It's only about 30 miles away. These places all have harbors where are the boats are. Lots of $$$ incentive to build. I think it was all done by The Army Corp of Engineers - back in the days when the government was looking to expand shipping and business related growth.