NAUI Advanced Scuba Diver
44 Night and Limited Visibility Diving
FIGURE 4-7. It is important that buddy lines be hand held and not made fast with a knot or clip, in case of entanglement.
through chemical reaction. A glass tube of one chemical
is sealed inside a plastic tube containing another chemical.
Bending the outer plastic tube until the glass tube
inside breaks allows the chemicals to mix and produce
light. Safety lights make it easy to spot divers in and
under the water, and their use is highly recommended
on all night dives (figure 4-6). In many locations using
them is standard practice and considered a requirement.
However, they are really only “marker” lights and do not
produce sufficient light to be useful for other purposes. Be
sure to wait to activate the safety light until just before you
begin the dive.
Luminescent gauges are preferred for night diving.
A luminescent gauge will “store” light energy from a dive
light that is shined on it and glow for many minutes. It
is unusual to find gauges that do not have luminescent
properties or, in the case of dive computers, an ability to
illuminate the display.
Other useful equipment includes items that are
hopefully part of your regular gear set. These items
include a good dive knife, gloves, a diving compass,
and a whistle for surface signaling. A low-pressure BC
inflator allows buoyancy to be controlled with just one
hand, which is helpful, since one of your hands will be
occupied with a dive light. A surface float with a “down”
line is also recommended unless you are diving from a
boat. Consider attaching a glow light to the float. It is not
a good idea to carry additional gear such as a camera
until you have acquired training and are comfortable
while night diving.
Except for the use of dive lights, limited visibility
diving equipment needs are the same. A dive light might
be helpful, but back-up lights, surface marker lights,
and chemical glow lights are not required. The use of
a “Buddy Line,” a short line held between two divers to
maintain contact, is often helpful to prevent separation in
murky water (figure 4-7).
PROCEDURES AND PRECAUTIONS
Night diving can be every bit as enjoyable as diving
in the daytime. There are even advantages to diving at
night. It is cooler for gearing up, there usually are fewer
divers to stir up an area, and your light allows you to be
seen as well as to see. In order to enjoy the underwater
world, however, you do need to abide by the following
procedures and be aware of a few new hazards.
Night diving is usually better when done from a
boat, but shore dives are perfectly acceptable. However,
rock strewn entry areas profuse with plant life that makes
the footing treacherous even in daylight should be avoided
at night. The best shore diving areas are those where