Deep-Six Underwater Systems, Inc.
"Add Depth to Your Life"

Table of Contents

1 Pressure and Gases
2 The Face Mask
3 The Snorkel
4 The Fins
5 Weight Systems
6 The Knife
7 The Wetsuit
8 Pressure and Water
9 The Ear and Pressure
10 The Sinus and Pressure
11 The Stomach/Intestine and Pressure
12 The Lung and Pressure
13 Barotrauma caused by External Air Spaces
14 The Buoyancy Compesation Device (BCD)
15 The Scuba Cylinder
16 The Scuba Cylinder Valve
17 The Regulator
18 Density and the Diver
19 The 4 Gas Laws
20 Hand Signals
21 Carbon Monoxide Poisoning
22 Hyperventilation
23 Nitrogen Narcosis
24 Diver's Flags
25 Sound Underwater
26 Color Underwater
27 Decompression Sickness
28 Breathing Oxygen
29 Deep Diving
30 Thermoclines
31 Thunderstorms
32 Underwater Life
33 Open Water Dives
34 The Final Examination
35 The Environment
36 Advanced Course

26 - Color Underwater

     The light spectrum is well known. "ROY G. BIV" is an acronym used to remember the colors from one end to the other. From left to right the letters stand for: Red, Orange, Yellow, Green, Blue, Indigo, and Violet. A mixture of all the colors makes white light.  That is, if one were to take 7 flashlights, each of which was giving off one of the listed colors, and shine all the different colors on a white wall, the spot of light would be white! A white light, therefore, gives off all the colors.

     Water acts as a selective filter. If one were to suspend a white light above the surface of a tank of water that was 1000' deep, the colors from the white light would be filtered out selectively one-by-one. It is gradual. There is no abrupt interface. For example, most of the red is gone from the light after 10 feet. Some of the orange is gone. Less of the yellow is lost, etc. At 25' most of the orange is gone. At 35' most of the yellow is gone. This continues through the spectrum until all that is left is violet light and that fades out after hundreds of feet. So, at the bottom of this 1000' tank of water there would be little or no light!

     Selective filtration creates conditions that make diving interesting. If a diver is bleeding at 60', where there is no red light, the diver bleeds a greenish-black blood. Taking a photograph at 30' would result in most objects appearing green, blue, violet, or black. Taking the same photograph with a flash (white light) would reveal startling colors that were not seen by the diver. Remember, the selective filtering by water occurs in any direction. So a camera's flash will lose most of its true color effectiveness after a distance of as little as five feet! That is because the light would leave the camera, hit the object 5 feet away and then return to the camera. In that 10 foot travel distance most of the red would be gone and the orange would be diminished.

     Neon colors do not loose their color like spectrum colors do. This author has video photographed a red stripe on a wet suit turn to black as a diver descended. Neon red and "hot pink" still were sending out bright color at 100'. That is because they fluoresce. Ultraviolet is found after violet on the spectrum. It is invisible to humans. It, like violet, goes to extreme depths. When a neon color is struck by the invisible ultraviolet it glows.

     At the other end of the spectrum is the red light that is filtered out by water rapidly. Beyond the red light there is a part of the spectrum that humans cannot see but can feel. It is infrared. (In the far red.) It is also known as heat. That is the energy that one can feel standing in front of a fireplace even though all the hot air, smoke, and gases are going up the chimney. Heat energy travels at the speed of light. You thought red light had trouble going deep in water. Infrared cannot penetrate 1mm! So you might wonder how the oceans get warm if heat cannot get down into the water? It's not the heat from the sun that makes the oceans warm. It is all the colors that are selectively filtered by the water.  They are "captured" by the molecules of water and are converted to heat energy because the molecules are made to move faster.

     Carry a flashlight with you when you are scuba diving. Even a small light will reveal colors that are startling and would have gone unnoticed!

     The above information assumes the water has good visibility. Patty Ryan in the Sept./Oct. issue of Sportdiver, states that the theoretical visibility for distilled water is 242 feet. Seeing further than that underwater is not possible. There are several pollutants that decrease water's visibility and also change the color and color penetration. If the water has silt and/or clay in it, the visibility may drop to almost zero and will have a brownish color. There are times when a lake, such as Minnewaska in New York State, will have a beautiful blue water color with a visibility of 35 to 40 feet. A sudden thunderstorm may cause a runoff bringing clay into the lake. I have seen the visibility close to shore drop from 30 feet to 1 foot in several minutes! If the water has an excessive growth of algae the color of the water will be green. The more the algae, the darker the green and the less the visibility. Sometimes the growth is seasonal. Some bodies of water have great visibility in the winter, and when the summer visitors arrive the amount of human waste runoff increases promoting an algae bloom. There are other pollutants that color the water. Tannic acid, especially from pine trees, can color the water brown even though it may be clear. Rotting vegetation and iron may cause a brown color, and paper mill runoff can leave it looking similar to milk. 

Copyright Information about this text, DIVING WITH DEEP-SIX is as follows: Copyright 1996 - 2007 by George D. Campbell, III; President. All Rights Reserved. This file may be posted on Electronic Bulletin Boards for download, but may not be modified, printed for distribution, or used for any commercial purpose without the author's written permission. is using this material with the permission of Deep Six. The full version is available at:
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