CHAPTER 7 Scuba Air Diving Operations
Change A 7-13
Lines and Floats. A lifeline should be used when it is necessary to exchange
signals, keep track of the divers location, or operate in limited visibility. There are
three basic types of lifelines: the tending line, the float line, and the buddy line.
A single diver will be tended with either a tending line or a float line. When direct
access to the surface is not available a tending line is mandatory. A float line may
not be used.
The float line reaches from the diver to a suitable float on the surface. This float
can be a brightly painted piece of wood, an empty sealed plastic bottle, a life ring,
or any similar buoyant, visible object. An inner tube with a diving flag attached
makes an excellent float and provides a hand-hold for a surfaced diver. If a pair of
divers are involved in a search, the use of a common float gives them a rendezvous
point. Additional lines for tools or other equipment can be tied to the float. A
buddy line, 6 to 10 feet long, is used to connect the diver partners at night or when
visibility is poor.
Any line used in scuba operations should be strong and have neutral or slightly
positive buoyancy. Nylon, Dacron, and manila are all suitable materials. Always
attach a lifeline to the diver, never to a piece of equipment that may be ripped
away or may be removed in an emergency.
Snorkel. A snorkel is a simple breathing tube that allows a diver to swim on the
surface for long or short distances face-down in the water. This permits the diver
to search shallow depths from the surface, conserving the scuba air supply. When
snorkels are used for skin diving, they are often attached to the face mask with a
lanyard or rubber connector to the opposite side of the regulator.
Compass. Small magnetic compasses are commonly used in underwater naviga-
tion. Such compasses are not highly accurate, but can be valuable when visibility
is poor. Submersible wrist compasses, watches, and depth gauges covered by
NAVSUPINST 5101.6 series are items controlled by the Nuclear Regulatory
Commission and require leak testing and reporting every 6 months.
Submersible Cylinder Pressure Gauge. The submersible cylinder pressure gauge
provides the diver with a continual read-out of the air remaining in the cylinder(s).
Various submersible pressure gauges suitable for Navy use are commercially
available. Most are equipped with a 2- to 3-foot length of high-pressure rubber
hose with standard fittings, and are secured directly into the first stage of the regu-
lator. When turning on the cylinder air, the diver should should turn the face of the
gauge away in the event of a blowout. When worn, the gauge and hose should be
tucked under a shoulder strap or otherwise secured to avoid its entanglement with
bottom debris or other equipment. The gauge must be calibrated in accordance
with the equipment planned maintenance system.
An important early step in any scuba dive is computing the air supply requirement.
The air supply requirement is a function of the expected duration of the dive at a
specific working depth. The duration of the air supply in the scuba cylinders
depends on the depth at which the air is delivered. Air consumption rate increases