Why PADI advocates the use of the buddy system
The buddy system in use today for scuba diving came from a decades old water safety concept found in swimming and lifeguard training. It was adopted because it applied to diving and because it made good safety sense. Early support of buddy diving safety procedures was referenced by Jacques Cousteau.... The buddy system provides divers in training with a safety redundancy .. that diving alone simply cannot provide. PADI has, and will continue to, train divers using the buddy system based on its proven benefit to diving, divers and diving safety.
Safety:
The roots of the buddy system arise from diving and water safety. Early days of diver training heralded the buddy system as an important safety procedure because only through the buddy system could a diver reasonably expect to escape from entanglement, entrapment, out of air situations, disorientation, a head injury, chest pains, cramping and dozens more....
Can Solo Diving be done responsibly?
Yes, but let's be clear about what responsible solo diving is and what it is not. It requires experienced scuba divers willing to make the necessary commitment to train and equip themselves to accept the added risks involved. That is to say, a person with the required attitude and aptitude to pursue responsible solo diving. This is true in other adventure sport activities such as solo rock climbing.
It is important to clarify what responsible solo scuba diving is. PADI views it as a form of technical diving and not for everybody. To responsibly engage in solo scuba diving, a diver must first be highly experienced, have a hundred or so buddy accompanied scuba dives, be absolutely self-reliant and apply the specialized procedures and equipment needed to engage in the activity. This includes, but is not limited to redundant air sources, specialized equipment configurations, specific dive planning, and management of solo diving problems and emergencies. When solo diving is performed within this description, we see a place for it. Responsible solo diving is not diving alone without the mental discipline, attitude or equipment. That said, no amount of redundant equipment can effectively back up a diver's brain better than another individual.
What concerns does PADI have with regard to solo diving
... Diving alone reduces the chance of survival regardless of the problem. Since 1989, there were at least 538 fatalities where it was clear divers were either intentionally diving solo, or became separated from a buddy and were de facto alone.
PADI's position is clear; solo diving proponents should advocate responsible solo diving on its own unique merits, requisite training, and equipment needs and not through sensationalized attempts to disparage a proven safety system, that has served the majority of recreational scuba divers well.