Buoys are, in effect, floating sign posts for the mariner. Their color,
shape, number, light, or sound characteristic tell the mariner how to
transit safe water and avoid navigational hazards, and assist the mariner
in following the proper course.
Buoy symbols shown on charts (see
fig. 4-10) indicate the approximate position
of the buoy and of the sinker that moors
the buoy to the bottom. The approximate
position is used because it is difficult to
keep a buoy and its moorings in an exact
geographical location. These difficulties
include, but are not limited to, imprecise
Figure 4-10. Buoy symbol
methods of position fixing, existing atmospheric and sea conditions, and
variations in the seabeds slope and makeup. The position of the buoy
can be expected to shift inside and outside the area shown on the chart
because they are moored with excess chain. In addition, buoys and
sinkers are normally checked only during periodic maintenance visits,
which often occur more than a year apart.
Types of Buoys
There are many different types of buoys in our buoyage system, with
each type designed to meet certain requirements. All buoys assist
mariners during daylight hours, and those with light, sound signals, or
both, serve the mariner during darkness or periods of low visibility. The
following are the principal types of buoys you will encounter:
Spar buoys are cylindrical in shape and are often constructed from large
logs, which are trimmed, shaped, and appropriately painted. Some are
metal, plastic, or fiberglass.
Can buoys (fig. 4-11) are built such that the upper portion that you
observe resembles a can. These buoys are unlighted and will be painted
green or have green and red horizontal bands.
Nun buoys (fig. 4-11) are built such that the upper portion you observe
resembles a cone with a rounded tip. Like cans, these are also unlighted
and will be painted red or have red and green horizontal bands.
Spherical buoys are unlighted and are round in shape. These buoys are
painted with red and white vertical stripes.