Snorkeling is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped tube called a snorkel, and usually swimfins. In cooler waters, a wetsuit may also be worn. Using this equipment allows the snorkeler to observe underwater attractions for extended periods of time with relatively little effort.
It is a popular recreational activity, particularly at tropical resort and scuba diving locations. Snorkelling is also employed by scuba divers when on the surface, and search and rescue teams may snorkel as part of a water-based search.
The primary attraction of snorkeling is the opportunity to observe underwater life in a natural setting without the complicated equipment and training required for scuba diving, and without the exhaled bubbles of scuba-diving equipment. Snorkeling is also a means to an end in popular sports such as underwater hockey, underwater ice hockey, underwater rugby and spearfishing.
A snorkel is a tube around 30 centimeters long and with an inside diameter of between 1.5 and 2.5 centimeters, 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. The snorkel usually has a piece of rubber that attaches the snorkel to the outside of the strap of the diving mask since pushing the snorkel between the mask-strap and the head can cause the mask to leak.
The most common type of snorkel is a simple 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 backwards right before reaching the surface and exhaling till reaching or "breaking" the surface (Displacement method) and facing forward again (normal position), before inhaling the next breath. The displacement method expels water by displacing its presence in the snorkel, thereby clearing the tube of its contents; it is a more advanced technique that takes practice but uses less energy and clears the snorkel with much greater efficiency.
Some modern snorkels have a sump in the mouthpiece to allow a small volume of water to remain in the snorkel without being inhaled when the snorkeler breathes. Some also have a one-way output valve in the sump, which automatically drains the sump as it fills with water. A few snorkels have float-operated valves attached to the top end of the tube to keep water out when the snorkeler submerges, whilst more recent designs have a splash deflector on the top end that directs any water that splashes over the open tube to the outside of the tube, thereby keeping the user's mouth free from water.
Snorkels used to be sold with small "ping pong" balls in a cage mounted to the open end of the tube to prevent water ingress, though these are no longer sold nor recommended to be used since they are considered hazardous to the snorkeler. Similarly, diving masks with a snorkel built into them are considered unsafe and obsolete.
The maximum usable length of the snorkel tube is around 40 centimeters (about 16 inches). A longer tube would place the lungs in deeper water where the surrounding water pressure is higher and the lungs would 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. Snorkels also create what is called "dead air space"—when the user takes in a fresh breath, some of the previously exhaled air remains in the snorkel and is recycled into the lungs, reducing breathing efficiency and causing CO2 retention. The greater the volume in the device, the more this problem is exacerbated.
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, underwater formation or other submerged objects either to observe fish, plants, organisms and/or formations. Being non-competitive, snorkeling is less a sport and more a leisure activity.
Snorkeling requires no special training, only the ability to swim and to breathe through the snorkel. However, for safety reasons, instruction and orientation from a fellow "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). As with scuba-diving it is always recommended that one not snorkel alone, but rather with a "buddy", a guide or a tour group.
Some commercial snorkeling locations require snorkelers 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. A wetsuit of appropriate thickness and coverage is suggested as they do provide some buoyancy without as much resistance to submersion.
Experienced snorkelers often start to investigate amateur free-diving, which should be preceded by at least some training from a dive instructor or experienced free-diver.
Snorkelers should be aware that their backside can be exposed to the sun for extended periods and can burn badly (even if slightly submerged), without being noticed. Wearing appropriate covering such as a "rash guard" (in warmer waters), a wetsuit and/or sunblock will mitigate the risk of sunburn. Sunblock and lotions have the added advantage of minimizing stings from water-borne creatures such as jellyfish and other micro-organisms.
The greatest danger to snorkelers are small inshore and leisure crafts such as jet skis, speed boats and the like. A snorkeler is often submerged in the water with only the tube visible above. Since these crafts can ply the same areas snorkelers visit, the chance for accidental collision exists. Sailboats and windsurfers are especially worrisome as their quiet propulsion systems means the snorkeler may be unaware of their presence, unlike any motor-driven craft, as sound travels further and 4x faster underwater. A snorkeler may surface under one and/or be struck by such vessels. Unfortunately few places demarcate small craft areas from snorkelers, unlike regular bathers who may have areas marked by buoys. Snorkelers may therefore choose to wear bright or highly reflective colors/outfits and/or to employ dive flags to ease being spotted by boaters and others.
Dehydration is another concern. Hydrating well before going in is recommended, especially if one intends to go for several hours. Proper hydration also prevents cramps. Salts help retain fluids and hydrites will help prevent cramping.
Snorkelers can experience hyperventilation, which can lead in turn to “shallow water blackout″; snorkeling with a buddy (and being aware of the buddy's condition at all times) can help avoid this situation.
When snorkeling on or near coral reefs, care must be exercised to avoid contact with the sharp coral and its poisonous inhabitants, usually via protective gloves and by being careful of one's environment. Booties and surf shoes are especially useful as they allow trekking over reefs exposed by low tide, to drop offs or deeper waters of the outer reef.
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 5 meters (3 to 15 feet) are favored by snorkelers. Deeper reefs are also good, but repeated breath holding to dive to those depths limit the number of practitioners and raises the bar on fitness and skill level.