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Enjoy Little Cayman Diving at its Best!

The Reading Room


Digital Underwater Photography

As technology improves, digital cameras are getting smaller, more sophisticated and... cheaper! Major brands like Canon now offer their own underwater housings for select cameras, water-resistant to 40 meters and for a fraction of typical third-party manufacturers' prices. More and more divers are suddenly interested in underwater photography. Old timers are trading their good old Nikonos and Sea & Sea's for a new digital. We know, we have too.

With the endless possibilities of digital computer editing, underwater photography has taken a sharp new turn. It has become an entirely new art form in which the actual shot during a dive is merely the beginning of the creative process. One no longer has to rely on the expensive services of a professional lab to achieve professional results - to crop, enlarge, print, modify, enhance and distribute his work. Anyone who owns a computer now also owns a whole potential photo lab. The rest is up to each one of us. There is no limit to creativity. But while luck and a juicy budget will increase your chances of getting good results, the key ingredients remain the same as always: know your stuff and practice. And practice. And practice.

Of course, with a digital camera in your hand, mistakes are easily corrected and soon forgiven. There no longer is a need to wait until back at home to realize that all your Whale Shark shots have failed because your film was not properly loaded, or the settings were wrong. You can instantly review your work, discard what's obviously bad, save the rest for later analysis, and keep shooting while correcting your errors.

Still. There is no way around one thing: you MUST know your camera. You must be intimate with it. Take it out for a ride, talk to it, sleep with it, whatever it takes ;-) You must be able to operate it quickly, barely looking at it, and without having to wonder about the settings or how to instantly kill the auto flash for instance. To achieve this, only one way: read the manual over and over again, and then play with your camera. And practice.

There are a number of very basic rules to remember about digital underwater photography:

If you are not yet an addict, you can visit our modest photo album to get an idea of what underwater photography is about.

Wondering how you could possibly choose a model of digital camera among the hundreds available on the market? Browse through the extremely thorough camera reviews of the excellent - and impartial - Digital Photography Preview web site. We highly recommend it!

Or click on the following link to download the very smart DigiHelp file. It's a simple Windows help file that you can browse online or download to your computer for later reference; it covers a broad range of digital photography-related topics and will be of interest to beginners and advanced photographers alike.

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Flying After Diving

The following are DAN's recommendations for flying after diving. They are based on a maximum altitude exposure of 8,000 feet (or 2440 meters.) That's the max. cabin pressure of commercial airliners. The Twin-Otters and other non-pressurized aircrafts used by Cayman Airways and Island Air typically fly back to Grand Cayman at an altitude ranging from 6000 to 8000 feet (that's also a cabin pressure, there's just no pressurization).

A minimum surface interval of 12 hours is required after any single dive before ascending to altitude in a commercial jet airliner. Divers who intend to make daily, multiple dives over repetitive days should extend that surface interval to a minimum of 18 hours before flying. The greater the duration before the flight, the less likely decompression sickness is to occur. 18 hours is our in-house absolute minimum interval but basically, no p.m. diving if you're fllying a.m.

Extended surface intervals allow for additional off gassing and may reduce the likelihood of developing symptoms. For those diving heavily during an extended vacation, it may be a good idea to take a day off at midweek, or save the last day to buy those last-minute t-shirts.

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Exercise & DCI - Should one exercise before or after diving?

Nitrogen absorption and elimination is largely a matter of temperature and circulation. Gas exchange works very well at constant temperature. After diving when body tissues have been loaded with nitrogen, activities such as running, weight lifting or a heavy workload can "shake up the bottle of soda", so to speak. So exercise after diving requires that you give tissue nitrogen levels time to drop, making bubbling generation less likely in the tissues. You should always start off a dive well rested with your muscles cooled down and not calling for more oxygen and blood flow.

We typically enter the water being warm and take on nitrogen at a standard rate. Once in the water we begin to cool, vasoconstrict, and take on less nitrogen. Which means that after the dive, we are still cool and not off gassing as a mathematical model may predict. This would appear to favor a diving after exercise procedure rather then the opposite. According to Dan, an altitude study done in the 90’s by Mike Powell Ph.D., found that if you waited 2 hours to go to altitude after doing a series of deep knee bends, the number of Doppler bubbles produced at altitude deceased to a baseline level after a two hour wait.

Although there are no definitive answers, a two-hour wait might be considered a minimum waiting guideline for diving after exercise. A more conservative suggestion would be four hours to allow you body to cool down and rest before you add a nitrogen exposure.

Remember to re-hydrate after exercise. Although dehydration doesn't cause decompression illness, increased fluid losses decrease your off gassing efficiency, so be sure to get plenty of water on dive and exercise days.

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Equalizing Ears and Sinuses - Problems & Techniques

Middle ear and sinus barotrauma are the most common injuries associated with exposure to increasing and decreasing pressure. Descent in the water adds approximately one-half pound of pressure for each foot of descent and diminishes a similar amount on ascent. According to Boyle's Law, as the pressure increases on descent, the volume of a gas in an enclosed space decreases proportionately. As the pressure decreases on ascent, the volume of the gas increases proportionately. On descent it is imperative that all enclosed air filled spaces be equalized actively or passively. On ascent, the increasing volume usually vents itself naturally.

For equalization to be effective, you should be free of nasal or sinus infections or allergic reactions. The lining of the nose, throat and Eustachian tubes should be as normal as possible. If this is true, the following techniques are effective in reducing middle ear and sinus squeeze.

Prior to descent, neutrally buoyant, with no air in your buoyancy compensator, gently inflate your ears with one of the techniques listed below. This gives you a little extra air in the middle ear and sinuses as you descend.

Descend feet first, if possible. This allows air to travel upward into the Eustachian tube and middle ear, a more natural direction. Use a descent line or the anchor line.

Equalize gently every few feet for the first 10 to 15 feet.

Pain is not acceptable. If there is pain, you have descended without adequately equalizing.

If you do not feel your ears opening, stop, try again, perhaps ascending a few feet to diminish the pressure around you. Do not bounce up and down. Try to tilt the blocked ear upward.

If you are unable to equalize, abort the dive. The consequences of descending without equalizing could ruin an entire dive trip or produce permanent damage and hearing loss.

If at any time during the dive you feel pain, have vertigo (the whirlies) or note sudden hearing loss, abort the dive. If these symptoms persist, do not dive again and consult your physician.

Equalizing Techniques

Valsalva - increase nasopharynx pressure by holding nose and breathing against a closed glottis (throat);

Toynbee - swallowing with mouth and nose closed - good for ascent!

Frenzel - Valsalva while contracting throat muscles with a closed glottis;

Lowry - Valsalva plus Toynbee - holding nose, gently trying to blow air out of nose while swallowing - easiest and best method!

Edmonds - jutting jaw forward plus Valsalva and/or Frenzel (good method);

BTV (Béance Tubaire Volontaire - Voluntary Tubal Opening) - Described by the French doctor Georges Deloncas, the BTV is a hands-free technique mostly used by free divers because it is very efficient even during a fast descent. Deloncas reported that a small percentage of divers (around 30%) are actually able to train their throat muscles to contract and open the Eustachian tubes on demand, as a prolonged action and not a simple spasm. The tubes' shape must be near perfect and a lot of training is required; it is, however, the ideal solution since it frees both hands, is none-forceful and works as well during descent and ascent;

Miscellaneous - swallowing, wiggling jaws - good for ascent!

Difficulty equalizing the air spaces of the middle ear and sinuses is the most common problem and injury among recreational divers. If you're experiencing problems with equalizing, the first thing to do is consult with your personal physician or an ear, nose and throat specialist who can evaluate your problem. Believe it or not, it may be something as simple as a chronic inflammation from allergies to household plants or pets. The irritation and inflammation resulting from an allergy can narrow the air passages and restrict the flow of air in and out of the middle ear.

Finally, remember to clear before you get into the water. You may also need to simply add something new to your current clearing technique, such as clearing as often as every 1 to 2 feet in order to prevent further difficulty. Make sure that when clearing you do it gently and before the problem becomes severe. Waiting too long will cause unnecessary pain, and a forceful clearing attempt by pinching your nose at that time may cause middle ear damage. Several gentle maneuvers and switching back and forth between swallowing and pinching your nose and gently blowing may be the ticket to a trouble-free dive. Above all, if you cannot equalize, then abort the dive.

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Asthma and Scuba Diving

In general, asthma is a lung disorder in which there is a tendency for the muscle surrounding the bronchi (breathing tubes) to contract excessively, causing narrowing, or broncho-constriction. As a result, this causes increased breathing resistance, which can manifest as wheezing, chest "tightness", cough, or breathlessness. In asthmatics, broncho-constriction can be precipitated by exposure to allergens, noxious fumes, cold air, exercise or respiratory infections such as a "cold". People with asthma may experience broncho-constriction due to more than one of these factors, but many asthmatics will experience a measurable increase in breathing resistance after exposure to any one or several of them. The increase in breathing resistance caused by bronchial narrowing may be compounded by the accumulation of mucus within the airways.

Serious potential risks may make scuba diving, which is often performed in isolated locations and far from competent medical care, an unwise elective sport for an individual with asthma. There are primarily two issues.

During scuba diving the diver experiences a reduction in breathing capacity due to the effects of immersion and an increase in breathing resistance caused by the higher gas density at depth. At 33-feet underwater, the maximum breathing capacity of a normal scuba diver is only 70-percent of the surface value. At 100-feet underwater, this reduction is approximately 50-percent. If, for example, a diver’s breathing capacity is already reduced because of asthma, there may not be sufficient reserve to accommodate the required increase demanded by exertion.

Both narrowing of the bronchi and excessive mucus production can inhibit exhalation of air during ascent, and could predispose the diver to pulmonary barotrauma leading to pneumothorax, pneumo-mediastinum and/or arterial gas embolism.

For these reasons, physicians trained in diving medicine have traditionally recommended that people with asthma should never dive. However, a consensus of experts at a 1995 workshop held under the auspices of the Undersea and Hyperbaric Medical Society (UHMS) proposed more liberal guidelines. Essentially, the UHMS workshop panel felt that the risk of diving is probably acceptable if, the diving candidate with some asthmatic ‘history’ demonstrates normal pulmonary function at rest (FVC, mid-expiratory flow, FEV1, FEF 25-75) and then again after strenuous exercise. It was also concluded that the degree of competency in making a medical assessment of diving fitness is enhanced if the examining doctor has relevant knowledge or experience of the diving environment and its associated hazards.

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Bladder Discomfort (Aka the "I'm Checking the Current Syndrome")

The key to this all too common issue is based on an understanding of dive physiology. The phenomenon is known as immersion diuresis and occurs whenever the body is emerged in water. Immersion, along with a water temperature that is colder than air, causes narrowing of the blood vessels in the extremities. This vasoconstriction occurs primarily in the skin and superficial tissues of the body as well as in the muscles of the arms and legs. The result is an increased volume of blood sent to the core organs of the body such as the heart, lungs and large internal blood vessels.

The hormone that controls the production of urine by the kidneys is called antidiuretic hormone (ADH). It controls when and how much urine your kidneys make. The increased blood volume to the major vessels is interpreted by your body as a fluid overload. This overload causes ADH production to stop, which in turn allows the kidneys to immediately produce urine to lower the centrally circulating blood volume; that's the body's automatic response to preserve blood volume. Once you exit the water, circulating blood volume returns to near normal - less the fluid taken to produce urine, which is quickly replaced as the body draws fluid from body tissues, such as muscles.

Unfortunately, you probably will also leave the water with a full bladder. Since wet suits are sacred tools (and rightly so) for most people, the best course of action remains a quick jump back in the water after the dive...

If your coffee is caffeinated, you may wish to switch to a decaffeinated brand, as caffeine is a known diuretic that also interferes with the production of ADH.

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Here is a collection of links pointing to interesting articles on different topics:

About Medical forms/waivers
Can the Truth Hurt?: Is It Dangerous to be Totally Honest on the Dive Medical Questionnaire? A DAN article summarizing this important issue.

Menstruation and DCI
An interesting DAN article about the research being conducted on the correlation between menstruation and DCI (Decompression Illness).

Cayman Islands Marine Parks
Marine Parks, Replenishment Zones, Environmental Zones and Animal Sanctuaries have been set up on the Islands to ensure that Cayman's treasures will be in pristine condition for generations of visitors to enjoy. Read the details in this Dive Cayman feature.

Little Cayman Nature
Share the Natural Wonders of the Caribbean. A web site with a nature-oriented description of the island.

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