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Aids to Navigation

Navigational Buoys are an important aspect of boating safely since they define safe and unsafe areas of transit for boats.  Aids to Navigation or ATONs, are most commonly seen in coastal areas of the United States but are also seen on inland waters.  

The most common and important buoys are the red and green buoys that define channels.  These buoys also have distinctive shapes and numbering.  Some have flashing lights and certain sounds so as to distinguish them from other nearby buoys, even in fog or at night.
  Entrance to Emerald Bay

Emerald Bay at Lake Tahoe has navigational buoys at its entrance. Even at this distance, the red buoy on the starboard side and the green buoy on the port side of this stern wheeler are apparent.

The buoys define the channel a boater must travel to safely enter this bay.  The old mnemonic is "Red, Right, Returning".  This means as you return from the ocean or bigger waters, such as the main part of Lake Tahoe, you should keep the red buoys on your right as you return into the harbor or bay.  The green buoys should be kept to your left as you enter the bay. The area between the red and green buoys is the safe channel for passage into the bay or harbor.

Green Can BuoyGreen, "can" buoys define the port side (left) of the channel.  They are can shaped with the longest part of the can oriented vertically.  They are numbered with odd numbers. The buoy above is number 3.  The entrance to a harbor may start many miles out.  The first green buoy is numbered one and increases as you proceed down the channel. This buoy has a lifting ring on the top for servicing by local authorities or the Coast Guard.  The buoys are anchored to the bottom of the bay with a long chain tied to a heavy weight such as a concrete block.


Nun Buoy

"Nun" buoys have a conical shape, are red in color and are even numbered.  They define the starboard or right side of the channel.  Like the can buoys, they may be first placed many miles off shore and the numbers increase as you proceed down the channel.   A nautical chart will allow you to calculate the heading needed to proceed down the channel.

Red and Green buoys such as those above, typically have the nun and can shapes since they are not lighted.  Buoys may also be lighted, or produce sounds.  It is important to recognize a buoy on a nautical chart since this will allow you to maintain a safe course.


Salmon Banks BuoyThe buoy listed on this excerpt from a nautical chart shows a buoy in the left lower quadrant.  The GPS marker with the green box of coordinates points to the buoy.  

All buoys are marked by a diamond shape attached to an open circle.  If there is a magenta color overlying the circle it means that the buoy is lighted.  Next to the buoy are the symbols:

G "3" This means that this is a green buoy with the number 3 on it.

The next line is: Fl  G  4s. This means that the buoy flashes a green light every 4 seconds.  Finally, the buoy also produces a sound.  For this particular buoy, it produces a gong sound. Each of these is important.  For example, if it was night time and the buoy was not visible, you would still be able to identify it by it's green flashing light every 4 seconds.  Even if it were night and foggy, you could hear the gong.

The entry buoys to Emerald Bay, Buoys 1 and 2 are illuminated so that boaters may find this narrow, and shallow entrance.