NAUI Advanced Scuba Diver
46 Night and Limited Visibility Diving
Your depth gauge should also be checked frequently as
you descend. Buoyancy control is just as important as on
any daylight dive. Adjust for neutral buoyancy so you can
stay clear of the bottom. This will keep you from bumping
into the reef or bottom dwelling animals and stirring
up silt (figure 4-8).
Once submerged and on your way, the following
procedures and precautions become important:
1. Keep excursions short. It is neither necessary nor
wise to cover large areas during a dive at night.
Enjoy the small things.
2. Monitor your air supply, direction, and buddy
more frequently than usual. It is easier to stay
together than it is to find each other at night. Be
sure to surface with an adequate reserve of air in
your cylinder in case your underwater navigation
is off.
3. If separated from your buddy, remain stationary
and turn slowly in a circle while looking for your
buddy’s light or glow light. If unsuccessful, move
in the direction in which your buddy was last
seen, stop and look again for light. If your buddy
is not located within one minute, ascend to the
surface, looking about as you ascend. Once at the
surface, continue to look for your buddy while
turning completely around with your light off. Do
this for one full rotation at the surface and again
while looking underwater toward the bottom. It
will be easier to see the glow of your buddy’s locator
light or glow stick with your dive light turned
off. Your buddy should be duplicating your
actions, so you should be able to reunite quickly
and continue your dive.
4. Be sure to keep your light beam out of the eyes
of other divers. Shining your light in their eyes
compromises their night vision for a short period.
When you shine a light toward other divers, point
it toward their waists.
5. If your light fails while diving, there is no cause
for alarm. Your buddy has a light and you should
both have back-up lights. First, make sure your
primary light is really defective by checking the
switch and by shaking the light. If the light is
inoperative, switch to your back-up light and finish
the dive. Even if all of your lights fail, you can
still make a normal ascent. By remaining calm on
the bottom and allowing your eyes to adjust to the
darkness for a couple of minutes you will find that
there is usually enough available light to allow
you to see things dimly. You and your buddy can
then ascend and terminate the dive.
6. Control your anxiety. Night diving may seem
spooky at first. But this can be half the adventure!
Moving shadows created by your light will
soon cease to startle you. You may see a surprised
animal trying to get away from the brightness of
your lights. As you become interested in things,
your anxieties will lessen. Take it easy and enjoy
yourself.
When you and your buddy agree to ascend, it is best
to do so on the line you used for descent. If the line can’t
be found, you can ascend without becoming disoriented
by holding your depth gauge in front of you in one hand
and shining your light on the gauge and your exhaust
bubbles as you ascend. The gauge helps you determine
your ascent rate, and the bubbles provide an up and
down reference.
As a general rule that applies to most dive excursions,
all of your equipment should be kept in place until
you are clear of the water after a dive. This will help prevent
the loss of gear.
The procedures and precautions for night dives also
apply to limited visibility dives except for use of lights. A
dive light can be useful in murky water, but it may help
to hold the light to one side to reduce the glare from light
reflected off particles suspended in the water (“backscatter”).
Perhaps the best use of a light in limited visibility is
for examining objects at close range. Other limited visibility
procedures include moving slowly and with one hand
extended in front of you. In extremely turbid water, it is
necessary to feel your way along the bottom, but diving
in such conditions is not usually enjoyable, and a dive
should be aborted if the visibility is that poor. Use of a
buddy line or holding hands can help prevent separation.
Disorientation can be even more of a problem in turbid
water than in clear water at night. The use of a descent/