During the autoscroller section that fills the room with water, before reaching the buoy, you have (barely) enough time to climb up the ladder first, walk to the left, jump on the slope, surf on the water and reach the plank above the buoy. Only perform it, if you know how to do it, it can destroy a good run.
There are other Buoy Swags in the game, and once documented, will be added to this page.