NAUI Advanced Scuba Diver
40 Night and Limited Visibility Diving
LEARNING GOALS
In this chapter you will:
1. Learn the basic procedures for limited visibility
and night diving.
2. Understand the attraction that limited visibility
and night diving have for many divers.
3. Learn about the equipment used in limited visibility
and night diving activities.
4. Learn the special signals and communication
challenges of limited visibility and night diving.
5. Understand the precautions associated with limited
visibility and night diving.
6. Explore a typical Advanced Scuba Diver course
limited visibility and night dive.
INTRODUCTION
You may be wondering why anyone would want to
plunge into inky black waters at night or dive when the
visibility is hardly an arm’s length. When you find out
why, you may become just as excited about night and
limited visibility diving as the thousands of enthusiasts
who enjoy these activities regularly (figure 4-1).
Night diving has a special fascination and mystique,
but this only supplements the real motives for descents
into darkness. One attraction of night diving is the opportunity
to view aquatic animals. Many of them that flee
upon sight or keep their distance during day-
light hours can be approached quite closely during nocturnal
dives. Because much of the life underwater is
nocturnal, you also get to see animals that you might not
encounter during daytime dives.
By using a dive light at close range, you also get
to appreciate the rich, vibrant colors of the sub-aquatic
world at night. With no dilution from natural lighting,
the colors appear more intense than at any other time.
Your narrow beam of light also focuses your attention so
your awareness of detail is increased. Night diving is an
excellent way to enjoy the beauty of the underwater world.
Limited visibility diving may not seem as attractive
as night diving, but in many areas visibility is always limited.
Visibility underwater is considered limited when you
cannot distinguish another diver at a distance of 3 meters
(10 feet) or less in a horizontal direction. There are many
things of interest in murky waters – wrecks, artifacts,
fossils, etc. – and the only way to get to see them is to
know the procedures for diving under these conditions.
Turbid water is frequently nutrient-rich water. Life is
often abundant in areas where the visibility is reduced by
the vast amount of nutrients, but the animals that abound
make diving in such areas exciting and enjoyable (figure
4-2).
Your instructor will introduce you to the techniques
for diving at night and for diving in turbid water, but
don’t expect to be proficient at either as a result of this
orientation. Your night diving ability will be limited to
circumstances similar to those in which you make your
introductory dive. Because such dives are usually conducted
in clear, calm water; at a protected, previously
FIGURE 4-1. Night diving is an activity regularly enjoyed by thousands
of divers.