Underwater diving is one of the active outdoor activities, which involves going underwater with special breathing apparatus (scuba diving) or by breath-holding (free diving). Diving with an aqualung is divided into types depending on the purpose of immersion. Among the types of scuba diving are the commercial (laying the communications, lifting the sunken objects), military, techno-diving (using different gas mixtures that allow reaching the depths of more than 40 m). But the most popular is an amateur or recreational diving. Most people with a good state of health can go for diving, but only after special training and receiving the international certificate of CMAS, PADI (Professional Association of Diving Instructors) and others.

Diving is an exciting type of active recreation, which allows discovering the secrets of the underwater world with one’s own eyes. The bottoms of many waters hide something unique, special, inaccessible, which attracts the fans of diving. Ships and aircrafts of the war times, underwater cliffs, whole villages and ancient cities – all these objects represent a separate world, the mysteries of which you can touch and feel while diving. Since man is not adapted to the aquatic environment, staying under water can be dangerous even with an aqualung. The greatest danger to human health is connected with a significant pressure differential (different barotraumas) and the danger of suffocation. The system of divers’ certification stipulates for a phased study of diving with an aqualung. Taking the first dives independently without a qualified instructor is life-threatening.

While describing diving as a form of active leisure, such types of it as free-diving and snorkeling should be mentioned. Free-diving is diving without any breathing devices. In this case a diving mask, fins and a belt with some burden can be used. Snorkeling (from a German word “Schnorchel” - a tube) is swimming on the surface of water with a mask and a snorkel. Snorkeling allows discovering the shallow seabed with relatively little effort and without special equipment, that’s why this type of active recreation is affordable and widespread. The best conditions for snorkeling are shallow waters with minimal waves, warm water and a various bottom. Tropical and equatorial latitudes are best suited for swimming with a mask and a snorkel, especially the coasts with coral reefs.