cave diving and the nss - bei Swiss-Cave-Diving

LIGHT SIGNALS 7
Chapter Three
LIGHT SIGNALS
A photographer we know has a sign outside his darkroom that
reads, "Caution: Keep door shut or all of the dark will leak out."
He claims that occasionally somebody'll fall for it. Well, be that as
it may, it is true that occasionally people who know nothing about
caves will ask, seemingly seriously, "You mean it's possible to cave
dive at night? But doesn't it get awfully dark inside the cave?" (Uh,
right. . . What college did you say you graduated from?)
But it's probably not fair to be too hard on them. After all, a
lot of fairly intelligent people seem to have difficulty with the concept
that what qualifies as a "cavern" dive* during the daytime, becomes
a full-blown "cave" dive** at night. A lot of people also seem to
have difficulty grasping the idea that small lights, which are adequate
for night diving and cavern diving, are only good enough to
be used as emergency backup lights for cave diving.
Cave-diving generally requires at least one very bright light,
which we refer to as the "primary light." With a good primary, a
cave with white or light-colored rock will be astonishingly well illuminated.
A bright, powerful light also makes it easier to keep
track of the line without having to be right on top of it at all times,
to reference the cave passageways in both directions, to plan your
swimming and buoyancy strategies well in advance, to keep tabs
on your buddies, to have your buddies keep tabs on you, and to
attract your buddies' attention should you need to.
But because primary lights are so bright, it is especially important
to avoid temporarily blinding and destroying your buddies'
night vision. Care must always be taken not to shine your light
* which we define as a dive within the natural daylight zone of the cave
** a dive which is beyond the reach of daylight
directly at your buddy's face. If
you see your buddy looking in
your direction, you can point your
light down or off to the side to
spare him the full force of the
glare. This can be hard to
remember to do sometimes when
you are focused in on some other
engaging task. But with frequent
mental review it can become
practically an instinctive habit.*
Care should also be taken
not to make too many unnecessary,
random, jerky movements
with your light. These can be mistaken for light signals. If your
light is constantly flashing around carelessly, your buddy will learn
to ignore it, and when you really do need to get his attention, you
may find yourself in the unfortunate position of the boy who cried,
"Wolf!" Good cave divers try to keep their normal light movements
smooth, slow, and controlled.
With this in mind, suppose you notice that your buddy behind
you seems to be making light movements which, while they are
clearly not a direct signal, are definitely more erratic than normal.
As an alert partner, you will want to observe him more closely to
determine if he is just making some minor adjustment or if this
might be the prelude to a more difficult situation. Typically, the diver
isn't concerned enough to formally signal you and halt the dive.
But if you're alert, you can slow down and let him see that you're
watching him and willing to pause for a moment if he so desires.
An important part of communicating underwater in a cave is
being receptive to the communication in the first place. You can't
just swim along in a coma and forget that your buddies exist. Being
a good buddy is a lot like being a good friend: you have to meet
your friends half way; you have to listen, not just hear. You have
to care about the other divers—the other people—you're with,
* Divers who wear their lights attached to their helmets may have a more difficult
time of this, because of the horse-blinder effect of masks, which makes it hard
to see things without turning your head, and thus your helmet and light, directly
towards them.