Snorkeling (British and Commonwealth English spelling: snorkelling) is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped breathing tube called a snorkel, and usually swimfins. In cooler waters, a wetsuit may also be worn. Use of this equipment allows the snorkeler to observe underwater attractions for extended periods with relatively little effort and to breathe while face-down at the surface.
Snorkeling is a popular recreational activity, particularly at tropical resort locations. The primary appeal is the opportunity to observe underwater life in a natural setting without the complicated equipment and training required for scuba diving. It appeals to all ages because of how little effort there is, and without the exhaled bubbles of scuba-diving equipment. It is the basis of the two surface disciplines of the underwater sport of finswimming.
Snorkeling is also used by scuba divers when on the surface, in underwater sports such as underwater hockey and underwater rugby, and as part of water-based searches conducted by search and rescue teams.
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History
Snorkeling is mentioned by Aristotle in his Parts of Animals. He refers to divers using "instruments for respiration" resembling the elephant's trunk. Some evidence suggests that snorkeling may have originated in Crete some 5,000 years ago as sea sponge farmers used hollowed out reeds to submerge and retrieve natural sponge for use in trade and commerce.
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Snorkel
The snorkel may be a separate item or may be integrated with a full-face snorkelling mask. The integrated system is only suitable for surface snorkelling, but the separate snorkel may also be used for free-diving and for surface breathing with scuba equipment.
A swimmer's snorkel is a tube typically about 30 centimeters (1 ft) long and with an inside diameter of between 1.5 and 2.5 centimeters (0.6 and 1 in), usually L- or J-shaped and fitted with a mouthpiece at the lower end, and constructed of rubber or plastic. It is used for breathing air from above the water surface when the wearer's mouth and nose are submerged, facing down. The snorkel may have a piece of rubber or a plastic clip that attaches the snorkel to the outside of the strap of the diving mask. An alternative technique is fitting the snorkel between the mask-strap and the head, but this practice may increase the chance that the mask leaks, and of losing the snorkel.
The optimum design length of the snorkel tube is at most 40 centimeters (about 16 inches). A longer tube would not allow breathing when snorkelling deeper, since it would place the lungs in deeper water where the surrounding water pressure is higher. The lungs would then be unable to inflate when the snorkeler inhales, because the muscles that expand the lungs are not strong enough to operate against the higher pressure. The pressure difference across the tissues in the lungs, between the blood capillaries and air spaces would increase the risk of pulmonary edema.
Snorkels constitute respiratory dead space. When the user takes in a fresh breath, some of the previously exhaled air which remains in the snorkel is inhaled again, reducing the amount of fresh air in the inhaled volume, and increasing the risk of a buildup of carbon dioxide in the blood, which can result in hypercapnia. The greater the volume of the tube, and the smaller the tidal volume of breathing, the more this problem is exacerbated. A smaller diameter tube reduces the dead volume, but also increases resistance to airflow and so increases the work of breathing. Occasional exhalation through the nose while snorkeling will slightly reduce the buildup of carbon dioxide, and may help in keeping the mask clear of water. It may also increase fogging.
Flooding and clearing
The simplest type of snorkel is a plain tube that is allowed to flood when underwater. The snorkeler expels water from the snorkel either with a sharp exhalation on return to the surface (blast clearing) or by tilting the head back shortly before reaching the surface and exhaling until reaching or breaking the surface (displacement method) and facing forward or down again before inhaling the next breath. The displacement method expels water by filling the snorkel with air; it is a technique that takes practice but clears the snorkel with less effort, but only works when surfacing. Clearing splash water while at the surface requires blast clearing.
Some snorkels have a sump at the lowest point to allow a small volume of water to remain in the snorkel without being inhaled when the snorkeler breathes. Some also have a non-return valve in the sump, to drain water in the tube when the diver exhales. The water is pushed out through the valve when the tube is blocked by water and the exhalation pressure exceeds the water pressure on the outside of the valve. This is almost exactly the mechanism of blast clearing which does not require the valve, but the pressure required is marginally less, and effective blast clearing requires a higher flow rate. A few models of snorkel have float-operated valves attached to the top end of the tube to keep water out when a wave passes, but these cause problems when diving as the snorkel must then be equalized during descent, using part of the diver's inhaled air supply. Some recent designs have a splash deflector on the top end that reduces entry of any water that splashes over the top end of the tube, thereby keeping it relatively free from water.
Finswimmers usually don't use snorkels with a sump valve, as they learn to blast clear the tube on most if not all exhalations, which keeps the water content in the tube to a minimum as the tube can be shaped for lower work of breathing, and elimination of water traps, allowing greater speed and lowering the stress of eventual swallowing of small quantities of water, which would impede their competition performance.
A common problem with all mechanical clearing mechanisms is their tendency to fail if infrequently used, or if stored for long periods, or through environmental fouling, or owing to lack of maintenance. Many also either slightly increase the flow resistance of the snorkel, or provide a small water trap, which retains a little water in the tube after clearing.
Modern designs use silicone rubber in the mouthpiece and one-way clearing and float valves due to its resistance to degradation and its long service life. Natural rubber was formerly used, but slowly oxidizes and breaks down due to ultraviolet light exposure from the sun. It eventually loses its flexibility, becomes brittle and cracks, which can cause clearing valves to stick in the open or closed position, and float valves to leak due to a failure of the valve seat to seal. In even older designs, some snorkels were made with small "ping pong" balls in a cage mounted to the open end of the tube to prevent water ingress. These are no longer sold or recommended because they are unreliable and considered hazardous. Similarly, diving masks with a built-in snorkel are considered unsafe by scuba diving organisations such as PADI, BSAC because they can engender a false sense of security and can be difficult to clear if flooded.
Application of a grease to valve seats can aid in sealing, but it is mechanically washed away over time. A heavy application can cause valves to stick closed and trap grit (foul), which may cause the valve to leak.
Environmental fouling can be caused by beach sand or loose-floating plant or animal matter becoming lodged in the valve, preventing proper operation.
Although it may be easier to breathe through a snorkel while swimming or floating at the surface, clearing valves may fail, or the snorkel may be lost. If the snorkeler is competent at swimming without a snorkel, the risk of drowning in these circumstances is reduced.
Diving mask
Snorkelers normally wear the same kind of mask as those worn by scuba divers. By creating an airspace, the mask enables the snorkeler to see clearly underwater. All scuba diving masks consist of the lenses also known as a faceplate, a soft rubber skirt, which encloses the nose and seals against the face, and a head strap to hold it in place. There are different styles and shapes. These range from oval shaped models to lower internal volume masks and may be made from different materials; common choices are silicone and rubber. A snorkeler who remains at the surface can use swimmer's goggles which do not enclose the nose.
Full-face snorkel mask
Full face snorkel masks use an integral snorkel with separate channels for intake and exhaled gases ensuring the user is always breathing untainted fresh air whatever the respiratory effort. The main difficulty or danger is that it must fit the whole face perfectly and since no two faces are the same shape, it should be used with great care and in safe water. In the event of accidental flooding, the whole mask must be removed to continue breathing. It can only be used on the surface, or a couple of feet below since there is no way to equalise the pressure at greater depth. Trained scuba divers are likely to avoid such devices.
Applications of snorkeling
Snorkeling is an activity in its own right, as well as an adjunct to other activities, such as breath-hold diving, spearfishing and scuba diving, and several competitive underwater sports, such as underwater hockey and finswimming.
In all cases, the use of a snorkel facilitates breathing while swimming at the surface and observing what is going on under the water.
Scuba diving
A snorkel can be useful when scuba diving as it is a safe way of swimming face down at the surface for extended periods to conserve the bottled air supply, or in an emergency situation when there is a problem with either air supply or regulator. Many dives do not require the use of a snorkel at all, and some scuba divers do not consider a snorkel a necessary or even useful piece of equipment, but the usefulness of a snorkel depends on the dive plan and the dive site. If there is no requirement to swim face down and see what is happening underwater, then a snorkel is not useful. If it is necessary to swim over heavy seaweed which can entangle the pillar valve and regulator if the diver swims face upward to get to and from the dive site, then a snorkel is useful to save breathing gas.
Practice of snorkeling
Although donning a mask and snorkel and swimming in any body of water would technically constitute "snorkeling," by and large it is generally accepted that a "snorkeler" would don such gear and practice such activity within the vicinity of a reef, wreck, or other submerged objects, either to observe aquatic organisms including fish, algae, etc. or to look at rock formations. Being non-competitive, snorkeling is considered more a leisure activity than a sport.
Snorkeling requires no special training, only the ability to swim and to breathe through the snorkel. However, for safety reasons, instruction and orientation from an experienced snorkeler, tour guide, dive shop, or equipment-rental shop is recommended. Instruction generally covers equipment usage, basic safety, what to look for, and what to look out for, and conservation instructions (fragile organisms such as coral are easily damaged by divers and snorkelers). Some organizations recommend that for snorkeling safety one should not snorkel alone, but rather with a "buddy", a guide or a tour group.
Some commercial snorkeling organisations require snorkelers at their venue to wear an inflatable vest, similar to a personal flotation device. They are usually bright yellow or orange and have a device that allows users to inflate or deflate the device to adjust their buoyancy. However, these devices hinder and prevent a snorkeler from free diving to any depth. Especially in cooler water, a wetsuit of appropriate thickness and coverage may be worn; wetsuits do provide some buoyancy without as much resistance to submersion. In the tropics, snorkelers (especially those with pale skin) often wear a rashguard or a shirt and/or board shorts in order to help protect the skin of the back and upper legs against sunburn.
Experienced snorkelers may progress to amateur free-diving, which should be preceded by at least some training from a dive instructor or experienced free-diver.
Safety precautions
The greatest danger to snorkelers are inshore and leisure craft such as jet skis, speed boats and the like. A snorkeler is often submerged in the water with only the tube visible above the surface. Since these craft can ply the same areas snorkelers visit, the chance for accidental collisions exists. Sailboats and sailboards are a particular hazard as their quiet propulsion systems may not alert the snorkeler of their presence. A snorkeler may surface underneath a vessel and/or be struck by it. Few locations demarcate small craft areas from snorkeling areas, unlike that done for regular beach-bathers, with areas marked by buoys. Snorkelers may therefore choose to wear bright or highly reflective colors/outfits and/or to employ dive flags to enable easy spotting by boaters and others.
Snorkelers' backs, ankles, and rear of their thighs can be exposed to the sun for extended periods, and can burn badly (even if slightly submerged), without being noticed in time. The wearing appropriate covering such as a "rash guard" with SPF (in warmer waters), a T-shirt, a wetsuit, and especially "waterproof" sunblock will mitigate this risk.
Dehydration is another concern. Hydrating well before entering the water is highly recommended, especially if one intends to snorkel for several hours. Proper hydration also prevents cramps. Snorkelers who hyperventilate to extend sub-surface time can experience hypocapnia if they hyperventilate prior to submerging. This can in turn lead to "shallow water blackout". Snorkeling with a buddy and remaining aware of the buddy's condition at all times can help avoid these difficulties.
When snorkeling on or near coral reefs, care must be exercised to avoid contact with the delicate (and sometimes sharp or stinging) coral, and its poisonous inhabitants, usually by wearing protective gloves and being careful of one's environment. Coral scrapes and cuts often require specialized first aid treatment and potentially, emergency medical treatment to avoid infection. Booties and surf shoes are especially useful as they allow trekking over reefs exposed by low tide, to access drop-offs or deeper waters of the outer reef - this is, however, ecologically irresponsible.
Contact with coral should always be avoided, because even boulder corals are fragile.
Another safety concern is interaction and contact with the marine life during encounters. While seals and sea turtles can seem harmless and docile, they can become alarmed if approached or feel threatened. Some creatures, like moray eels, can hide in coral crevices and holes and will bite fingers when there is too much prodding going on. For these reasons, snorkeling websites often recommend an "observe but don't touch" etiquette when snorkeling.
Snorkeling locations
Snorkeling is possible in almost any body of water, but snorkelers are most likely to be found in locations where there are minimal waves, warm water, and something particularly interesting to see near the surface.
Generally shallow reefs ranging from sea level to 1 to 4 meters (3 to 13 ft) are favored by snorkelers. Deeper reefs can also be explored, but repeated breath-holding to dive to those depths limits the number of practitioners, and raises the bar on the required fitness and skill level. Risk increases with increased depth and duration of the breath-hold excursions from the surface.
- Bog snorkelling: An individual sport, popular in the United Kingdom and Australia.
- Finswimming: An individual sport, the most popular competitive sport of CMAS, the only of this federation present in World Games. Finswimmers use a slightly different snorkel, suited for hydrodynamics and speed.
- Free-diving: Any form of diving without breathing apparatus, but often referring to competitive apnea as a sport.
- Scuba diving: A form of untethered diving using a self-contained portable breathing apparatus, frequently as a pastime.
- Spearfishing: Fishing with a spear often with snorkelling equipment, either for competitive sport or to obtain food.
- Underwater hockey: A competitive team-sport played in swimming pools using snorkelling equipment, sticks and a puck.
- Underwater rugby: A competitive team-sport played in deeper swimming pools using snorkelling equipment, baskets and a ball.
Source of the article : Wikipedia
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