From Wikipedia: Snorkeling (British spelling: snorkelling) 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. Use of this equipment allows the snorkeler to observe underwater attractions for extended periods of time with relatively little effort. Snorkeling is a popular recreational activity, particularly at tropical resort and scuba diving 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 and it appeals to all ages because of how little effort there is, and without the exhaled bubbles of scuba-diving equipment. Snorkeling is also employed by scuba divers when on the surface, and search and rescue teams may snorkel as part of a water-based search. It is also a means to an end in popular sports such as underwater hockey, underwater ice hockey, underwater rugby and spearfishing. ~~~ A swimmer's snorkel is a tube typically about 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. An older technique is pushing the snorkel between the mask-strap and the head, but this practice increases the chances the mask will 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 back shortly before reaching the surface and exhaling until reaching or "breaking" the surface...