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The underwater environment

It's a different world down there


Deep-sea creatures are accustomed to the great water pressure around them. Underwater photographers need to take special precautions in this very different environment.
Deep-sea creatures are accustomed to the great water pressure around them. Underwater photographers need to take special precautions in this very different environment.

PRESSURE

The most significant difference between the environment above water (the land) and the environment below the surface of any sizeable body of water, including fresh water lakes, ocean depths and even swimming pools, is unquestionably pressure.

The pressure that matters to the underwater photographer - indeed to any diver - is the pressure created by the water surrounding him or her. It is relatively insignificant near the surface. The deeper the diver descends, the greater the water pressure exerted on his or her body.

Water's pressure is a result of its density, which is about 800 times greater than the density of air. Sea water has a density of 64 pounds per cubic foot. Compare that to the density of air at .08 pounds per cubic foot. Big difference.

Air pressure (atmospheric pressure) is 14.7 pounds per square inch (psi) when measured at sea level. Water pressure at sea level is the sum of atmospheric pressure plus .445 psi for average ocean water. Fresh water pressure is different - .432 psi + atmospheric pressure of 14.7 psi. Pressure increases by .445 psi in the ocean and by .432 psi in fresh water bodies for every foot of increased depth.


HOW DOES WATER PRESSURE AFFECT THE UNDERWATER PHOTOGRAPHER?

There are several ways in which an underwater photographer is affected by increased water pressure.

Water pressure tends to cause the diver's Eustachian tubes to close, preventing pressure equalization across the ear drum, with painful results. Divers are trained to equalize the pressures in their bodies as they descend deeper into water. They must, for example, "clear" their ears as they descend, just as airplane passengers swallow to equalize their ear pressure with the pressure inside the aircraft.

Divers are taught to perform the "Valsalva" maneuver which involves closing their lips, pinching their noses and then strongly exhaling, forcing air into the middle ear to relieve the pressure differential. But the diver whose hands are full of camera gear will not be able to pinch his or her nose, and must use an alternate method of pressure equalization, such as swallowing, enforced yawning, moving his or her jaw back and forth, and even snorting through the nose into the mask.

Underwater photography equipment must not only be waterproof; it must also be able to withstand the water pressure to which it will be subjected.
Underwater photography equipment must not only be waterproof; it must also be able to withstand the water pressure to which it will be subjected.

Another problem that requires a hands-free solution can occur when the diver-photographer's mask becomes filled with water. The diver must empty it out so he or she can properly see again, a tricky thing to do when your hands are filled with camera gear, but not impossible. It requires some practice. The diver must tilt his or her mask perpendicular to the surface, and exhale through his or her nose, causing an air build-up within the mask that will force the water out.

Water pressure can also affect a photographer's equipment. If the camera housing, for example, is not pressure-resistant for the depth at which it is being used, it will likely implode, wrecking the camera within and possibly even injuring the diver. All photography and lighting equipment used underwater must not only be waterproof, but must also be able to withstand the water pressure to which it will be exposed.


TIME

Many shots require a good deal of patience in order to capture an underwater creature in a particular position or orientation. Patience calls for the availability of time.

The amount of time available for underwater photography is limited by the scuba diver's air supply, which decreases as depth increases. The snorkeling photographer is limited by how long he or she can hold his or her breath when swimming down to take a picture.

Successful underwater photographers have learned how to compose quickly and react as soon as the shot looks right. It is a big help to develop the ability to pre-visualize what you would like to photograph.

When descending to get close to a subject, the snorkeling photographer is limited by how long she can hold her breath
When descending to get close to a subject, the snorkeling photographer is limited by how long she can hold her breath

The creatures of the sea have adjusted to their environment, whether warm or cold. Underwater photographers need to take precautions to survive in what can be a hostile environment.
The creatures of the sea have adjusted to their environment, whether warm or cold. Underwater photographers need to take precautions to survive in what can be a hostile environment.

TEMPERATURE

The underwater photographer must protect himself or herself from hypothermia. Hypothermia can occur when the body is exposed to the colder temperatures of the surrounding water and its internal mechanisms are unable to replenish the body heat being lost. Heat is lost much more quickly in water than in air. Shivering is a symptom of the possible onset of hypothermia, and divers should get out of the water and warm up as soon as they begin to shiver. Signs and symptoms include gradual loss of mental and physical abilities. Severe hypothermia can lead to death. Judgement can be impaired by a drop in body temperature, and confusion can set in quickly if you do not get out of the water and seek warmth. Rewarming techniques can include removing a cold wet suit or swimwear and covering with warm, dry blankets. Drinking warmed fluids will help.

Water that is 70 to 80 degrees F. (21 to 26.5 C) can cool you down in an hour or two. You can begin to lose dexterity in as little as half an hour in water that is 60 to 70 degrees F. (15.5 to 21 C), and in about 15 minutes in water that is 50 to 60 degrees F. (15 - 21 C). As water temperatures drop below 50 degrees F, swimmers not wearing protective clothing won't last long before hypothermia sets in.


FATIGUE

Water density causes greater resistance than air density.

This resistance acting on the underwater photographer's body and bulky camera equipment as he or she moves in the water can bring on fatigue much more quickly than the diver might expect. Increasing speed underwater will increase resistance. Taking it slow and easy will reduce the possibility of fatigue and also help your air supply to last longer.

Water density causes greater resistance than air density. Moving slowly underwater preserves energy and air supply.
Water density causes greater resistance than air density. Moving slowly underwater preserves energy and air supply.