Lateral mark
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A lateral buoy, lateral post or lateral mark, as defined by the International Association of Marine Aids to Navigation and Lighthouse Authorities, is a sea mark used in maritime pilotage to indicate the edge of a channel.
A Region A lateral mark, showing both the green color and the triangular symbol, denoting the channel at the entrance to the Port River near Adelaide, South Australia
System A: Red port / green starboard marks when entering from sea into Le Palais, France
Buoy
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A buoy is a floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents.
Green can #11 near the mouth of the Saugatuck River (IALA region B).
Green Can #11 on a nautical chart
NOAA Weather buoy