Scuba Diving is a recreational diving where the diver uses a self-contained underwater breathing apparatus known as SCUBA. 

Scuba divers carry their own source of breathing gas, usually Air or Nitrox (21-40% Oxygen) allowing them longer underwater endurance than freedivers/breath-hold divers. 

Scuba diving may be done recreationally or professionally in a number of applications, including scientific, military and public safety roles, but most commercial diving uses surface-supplied diving equipment when this is practicable. Scuba divers engaged in armed forces covert operations may be referred to as frogmen, combat divers or attack swimmers.

Equipment includes fins, wetsuit, weight, bcd, regulator's, mask & snorkel. 

Scuba divers are trained in the procedures and skills appropriate to their level of certification by instructors affiliated to the diver certification organisations which issue these certifications.

These include standard operating procedures for using the equipment and dealing with the general hazards of the underwater environment, and emergency procedures for self-help and assistance of a similarly equipped diver experiencing problems.

A minimum level of fitness and health is required by most training organisations, but a higher level of fitness may be appropriate for some applications.