When using the buddy system, pairs and groups of three SCUBA divers dive together and co-operate with each other, so that they can help or rescue each other in the event of an emergency.

The system is a safety procedure that improves the divers' chances of avoiding or surviving accidents in or underwater. A pair of divers is the best combination in buddy diving: with threesomes, one of the divers can easily lose the attention of the other two. Groups with more than three divers are not using the buddy system. The system is likely to be effective in mitigating out-of-air emergencies, non-diving medical emergencies and entrapment in ropes or nets. When used with the buddy check it can help avoid equipment omission, misuse and failure.

With buddy diving, each of the divers is presumed to have a responsibility to the other. The "buddies" are expected to monitor each other, to stay close enough together to be able to help in an emergency, to behave safely and to follow the plan agreed by the pair before the dive. When the system fails, it is generally because one of the divers does not fulfil his or her responsibilities as a buddy.

Alternatives

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The two alternatives, solo diving and diving as an individual in a large group, have disadvantages when compared to the buddy system especially for the novice.

• Although solo diving is used by some divers in technical diving, it is only effective if the diver is totally self-sufficient. This is not possible in some cases, such as entrapment in ropes and nets and during non-diving medical emergencies.
• In group diving, especially in large groups, poor visibility or currents, weak individual divers can easily become detached from the group and lose the protection of any experienced divers in the group.

Other uses

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• A similar system of pairs is used during firefighting, where it is called the two-in, two-out principle.
• In computing, buddy system is often used as a synonym for buddy memory allocation.
• For participants in NaNoEdMo, buddy system refers to the mandatory practice of staying in touch with a partner who can give advice or help with editing if needed, and testify that 50 hours of work have been done.

Diving