Special marks buoys yellow buoys indicate key features or geography. They should be yellow and may have a cross/x as a top mark.  Often, they will include working or pictorial representations to inform you of their message.  They are giving you information about an area.  There is no specific shape but they must not be able to be confused with the shape of other marks.

They can be used extensively in racing, allocated water sports area, swimming and cables. 

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