0_Wizard
When you go scuba diving, they include extra cylinders for emergency breathing.
They may include additional cylinders for decompression gas or emergency breathing gas.
chosen_Scuba_diving_0
Scuba diving
chosen_topic_0_Scuba_diving
Scuba diving
Scuba diving is a form of underwater diving where the diver uses a self-contained underwater breathing apparatus (scuba) which is completely independent of surface supply, to breathe underwater. Scuba divers carry their own source of breathing gas, usually compressed air, allowing them greater independence and freedom of movement than surface-supplied divers, and longer underwater endurance than breath-hold divers. Open circuit scuba systems discharge the breathing gas into the environment as it is exhaled, and consist of one or more diving cylinders containing breathing gas at high pressure which is supplied to the diver through a regulator.
Scuba set
A scuba set is any breathing apparatus that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. (Scuba is an anacronym for self-contained underwater breathing apparatus.) Although strictly speaking the scuba set is only the diving equipment which is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense it has been used to refer to any diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment.
Underwater diving
Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done. In ambient pressure diving, the diver is directly exposed to the pressure of the surrounding water.
Diving cylinder
A diving cylinder, scuba tank or diving tank is a gas cylinder used to store and transport the high pressure breathing gas required by a scuba set. It may also be used for surface-supplied diving or as decompression gas or an emergency gas supply for surface supplied diving or scuba. Cylinders provide gas to the diver through the demand valve of a diving regulator or the breathing loop of a diving rebreather. Diving cylinders are usually manufactured from aluminium or steel alloys, and are normally fitted with one of two common types of cylinder valve for filling and connection to the regulator.
Scuba skills
Scuba skills are the skills required to dive safely using self-contained underwater breathing apparatus, (scuba). Most of these skills are relevant to both open circuit and rebreather scuba, and many are also relevant to surface-supplied diving. Those skills which are critical to the safety of the diver may require more practice than is usually provided during training to achieve reliable long-term proficiency  Some of the skills are generally accepted by recreational diver certification agencies as necessary for any scuba diver to be considered competent to dive without direct supervision, and others are more advanced, though some diver certification and accreditation organizations may consider some of these to also be essential for minimum acceptable entry level competence.
Surface-supplied diving
Surface-supplied diving is diving using equipment supplied with breathing gas using a diver's umbilical from the surface, either from the shore or from a diving support vessel, sometimes indirectly via a diving bell. This is different from scuba diving, where the diver's breathing equipment is completely self-contained and there is no link to the surface. The primary advantages of conventional surface supplied diving are lower risk of drowning and considerably larger breathing gas supply than scuba, allowing longer working periods and safer decompression. The copper helmeted free-flow standard diving dress is the version which made commercial diving a viable occupation, and although still used in some regions, this heavy equipment has been superseded by lighter free-flow helmets, and to a large extent, lightweight demand helmets, band masks and full-face diving masks.
Diving safety
The safety of underwater diving depends on four factors: the environment, the equipment, behaviour of the individual diver and performance of the dive team. The underwater environment can impose severe physical and psychological stress on a diver, and is mostly beyond the diver's control. Equipment is used to operate underwater for anything beyond very short periods, and the reliable function of some of the equipment is critical to even short term survival. Other equipment allows the diver to operate in relative comfort and efficiency. The performance of the individual diver depends on learned skills, many of which are not intuitive, and the performance of the team depends on communication and common goals.
1_Apprentice
That's important. There is surprisingly a great deal of safety knowledge required to scuba safely, such as rising slowly instead of too quickly.