Buoys were mentioned in issues 403, 450, 504, and 547 of the Club Penguin Times.
Buoy number 7 was also included in one of the Mix 'N Match Figures sets, along with a diver and a mermaid.
Trivia
Buoy number 4 could only be seen in Secret Missions, due to it appearing on the back wall of the Lighthouse, which was not visible in the main game.
During the Future Party, a buoy was used to for the head of one of the types of microbots, where the number displayed on the buoy could be any number ranging from 1 to 99.
Buoys 2 and 4 appeared in the files for level 3 of Jet Pack Adventure, but oddly did not appear within the game itself.