We saw a good example of why one should be careful about which mooring bouys they choose to tie yesterday afternoon at watmouth Bay on Lopez. A 30' motor yacht tied to one of four bouys that are marked private. The wind came up and I saw the buoy break loose. I layed on our horn and tried calling on vhf with no response. Their dingy was at another yacht. I was starting to pull anchor to try and notify them when a small research boat that had been on the beach headed out to find the owners. By the time the owners got to their boat it was a quarter mile out heading for Rosario strait. Turns out there were two teenage girls aboard when it broke loose. They didn't seem to know what had happened. I'm just glad that didn't happen in the middle of the night. Once they got control of the boat they promptly tied to another private bouy rather than use their anchor. Luckily it held for the night.