It covers the entire spectrum of recreational diving theory, including:
PADI is the world's largest and most respected scuba diving training organization, with over 6,000 dive shops and resorts worldwide. Founded in 1966, PADI has trained millions of divers, providing a standardized system of scuba diving education that emphasizes safety, fun, and environmental awareness. padi encyclopedia of recreational diving pdf
To most, it was a dense manual of gas laws and physiology. To Elias, it was a map to a hidden world It covers the entire spectrum of recreational diving