Training and Certification

Before taking a dive, enthusiasts must gain certification by passing a course offered by a certified scuba diving agency. All agencies require that participants be proficient swimmers, in reasonably good health, and at least 12 years old.

The course typically consists of classroom work, practice in a pool or other confined body of water, and dives in the open water, usually in a large lake or the ocean. In the course, students learn to use diving equipment, to equalize air pressure as they descend, to swim efficiently underwater, and to ascend safely. They also learn how to communicate underwater with hand signals.

Scuba diving should always be practiced with at least one other person, and partners should remain together throughout the dive. Certification courses teach divers the rules and advantages of the buddy system. Diving partners learn to double-check each other's equipment, share a single air supply, and assist one another should a problem occur. 

Controlling breathing rate is also important. During exercises in water, diving students practice breathing in a slow, continuous manner. Most hazards can be avoided if divers follow the safety procedures taught in certification courses and do not attempt dives beyond their ability and experience.

To become certified, diving students must pass a written exam and a swimming proficiency test, and successfully demonstrate newly mastered skills in four open-water dives. Proficient divers then receive a certification card that allows them to make unsupervised dives, refill air tanks, and buy diving equipment worldwide. Stores that sell diving equipment and businesses that operate diving tours require this proof of certification.

Scuba Diving
  

Saturation Diving
  
Commercial or scientific divers live in an pressurized chamber, for extended period, called saturation diving. The diver's body becomes saturated with gas mixtures corresponding to the working depth. Divers can therefore remain under a constant pressure for weeks or months, rather than go through a lengthy decompression during and after each dive. 

The hazards in saturation diving are much like the hazards of living in a space station. Inhabitants depend on life support systems for their air and power supply. Should medical or mechanical difficulties occur, a risky evacuation procedure that requires a series of decompression stops is the only way to bring divers to the surface safely.

Snorkeling
  
Is a common form of diving on the surface or just below on the surface. A snorkel is a tube that allows the diver to breathe while floating at the water's surface. One end fits in the diver's mouth and the other end extends above the water. 

Equalization
 
When a diver descend, the surrounding water pressure increases, causing a slight discomfort, or squeeze, in their ears and sinuses. Divers relieve this discomfort by holding their noses and blowing gently. This technique is called equalization as it equalizes the pressure within the divers' bodies with that of the surrounding water, allowing them to proceed safely.

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