Cited Passage
encounter a thermocline, substantial energy is lost. This
tends to isolate sound within water of a consistent tempera-
ture. Interestingly, a diver who is not in the same thermo-
cline range as the source of a sound often cannot hear that
sound, even though it is coming from only a few feet away.
Hearing under water is affected in important ways. It
is almost impossible to determine from which direction a
sound originates. On land, sound reaches one ear before
the other; thus, the direction of the source can be deter-
mined. Under water, sound travels so quickly it reaches
both ears without an appreciable interval. The sound
seems to originate from all directions. Sound travels
faster, seems non-directional, and is more easily heard
under water.
Physics of Diving 2-17
Water Condition
Murky, turbid water of low
visibility (rivers, harbors,
etc.)
Moderately turbid water
(sounds, bays, coastal
water)
Clear water (southern
water, deep water
offshore, etc. See note.)
Natural Illumination
Fluorescent yellow,
orange, and red
Regular yellow, orange,
and white
Any fluorescence in the
yellows, oranges, or
reds
Regular paint of yellow,
orange, and white
Fluorescent paint
Incandescent Illumination
Yellow, orange, red, and
white (no advantage in
fluorescent paint)
Any fluorescence in the yel-
lows, oranges, or reds
Regular paint of yellow,
orange, and white
Fluorescent paint
Mercury Light
Fluorescent yellow-green
and yellow-orange
Regular yellow, white
Fluorescent yellow-green
or yellow-orange
Regular yellow, white
Fluorescent paint
TABLE 2.8
Colors That Give Best Visibility Against a Water Background
NOTE: With any type of illumination, fluorescent paints are superior.
a. With long viewing distances, fluorescent green and yellow-green are excellent.
b. With short viewing distances, fluorescent orange is excellent.
The NOAA Diving Manual was prepared jointly by the National Oceanic and
Atmospheric Administration (NOAA), U.S. Department of Commerce and Best
Publishing Company.
This CD-ROM product is produced and distributed by the National Technical Information
Service (NTIS), U.S. Department of Commerce.
Visit our Web site at www.ntis.gov.
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