In underwater diving, open water is unrestricted water such as a sea, lake, river, or flooded quarry. It is a contradistinction to confined water where initial skills training takes place. Open water also means the diver has direct vertical access to the surface of the water in contact with the Earth's atmosphere. Open water diving implies that if a problem arises, the diver can directly ascend vertically to the atmosphere to breathe air. Penetration diving—involving entering caves or wrecks, or diving under ice—is therefore not "open water diving". In some contexts the lack of a decompression obligation is considered a necessary condition for classification of a dive as an open water dive, as a decompression obligation is a procedural and safety restriction on immediate ascent to the surface, but this does not affect the classification of the venue as open water.
Drift diving is a type of scuba diving where the diver is transported by the water movement caused by the tide, an ocean current or in a river. The choice whether to drift dive depends on the purpose of the dive, and whether there is an option. At some sites there is almost always a current running, and at others the strength and direction of water movement may vary with the tide, or other driving forces, like wind or recent rainfall. At some sites there may be considerable variation in visibility and underwater life activity based on the speed and direction of flow.
A divemaster (DM) is a role that includes organising and leading recreational dives, particularly in a professional capacity, and is a qualification used in many parts of the world in recreational scuba diving for a diver who has supervisory responsibility for a group of divers and as a dive guide. As well as being a generic term, 'Divemaster' is the title of the first professional rating of many training agencies, such as PADI, SSI, SDI, NASE, except NAUI, which rates a NAUI Divemaster under a NAUI Instructor but above a NAUI Assistant Instructor. The divemaster certification is generally equivalent to the requirements of ISO 24801-3 Dive Leader.
A surface marker buoy, SMB, dive float or simply a blob is a buoy used by scuba divers, at the end of a line from the diver, intended to indicate the diver's position to people at the surface while the diver is underwater. Two kinds are used; one (SMB) is towed for the whole dive, and indicates the position of the dive group throughout the dive, and the other, a delayed surface marker buoy, DSMB or decompression buoy, is deployed towards the end of the dive as a signal to the surface that the divers have started to ascend, and where they are going to surface. Both types can also function as a depth reference for controlling speed of ascent and accurately maintaining depth at decompression stops. Surface marker buoys are also used by freedivers in open water, to indicate the approximate position of the diver when submerged. They may also be used to support a catch bag or fish stringer by underwater hunters and collectors. A DSMB is considered by recreational scuba divers and service providers to be a highly important item of safety equipment, yet its use is not part of the entry level recreational diver training for all training agencies, and there are significant hazards associated with incompetent use.
Recreational diving or sport diving is diving for the purpose of leisure and enjoyment, usually when using scuba equipment. The term "recreational diving" may also be used in contradistinction to "technical diving", a more demanding aspect of recreational diving which requires more training and experience to develop the competence to reliably manage more complex equipment in the more hazardous conditions associated with the disciplines. Breath-hold diving for recreation also fits into the broader scope of the term, but this article covers the commonly used meaning of scuba diving for recreational purposes, where the diver is not constrained from making a direct near-vertical ascent to the surface at any point during the dive, and risk is considered low.
Diver communications are the methods used by divers to communicate with each other or with surface members of the dive team. In professional diving, diver communication is usually between a single working diver and the diving supervisor at the surface control point. This is considered important both for managing the diving work, and as a safety measure for monitoring the condition of the diver. The traditional method of communication was by line signals, but this has been superseded by voice communication, and line signals are now used in emergencies when voice communications have failed. Surface supplied divers often carry a closed circuit video camera on the helmet which allows the surface team to see what the diver is doing and to be involved in inspection tasks. This can also be used to transmit hand signals to the surface if voice communications fails. Underwater slates may be used to write text messages which can be shown to other divers, and there are some dive computers which allow a limited number of pre-programmed text messages to be sent through-water to other divers or surface personnel with compatible equipment.
Scuba diving is a mode of underwater diving whereby divers use breathing equipment that is completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The name scuba is an anacronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their own source of breathing gas, usually compressed air, affording them greater independence and movement than surface-supplied divers, and more time underwater than free divers. Although the use of compressed air is common, a gas blend with a higher oxygen content, known as enriched air or nitrox, has become popular due to the reduced nitrogen intake during long or repetitive dives. Also, breathing gas diluted with helium may be used to reduce the effects of nitrogen narcosis during deeper dives.
Scuba Schools International (SSI) is a for-profit organization that teaches the skills involved in scuba diving and freediving, and supports dive businesses and resorts. SSI has over 2,500 authorized dealers, 35 regional centers, and offices all over the world.
Solo diving is the practice of self-sufficient underwater diving without a "dive buddy", particularly with reference to scuba diving, but the term is also applied to freediving. Professionally, solo diving has always been an option which depends on operational requirements and risk assessment. Surface supplied diving and atmospheric suit diving are commonly single diver underwater activities but are accompanied by an on-surface support team dedicated to the safety of the diver, including a stand-by diver, and are not considered solo diving in this sense.
Diver navigation, termed "underwater navigation" by scuba divers, is a set of techniques—including observing natural features, the use of a compass, and surface observations—that divers use to navigate underwater. Free-divers do not spend enough time underwater for navigation to be important, and surface supplied divers are limited in the distance they can travel by the length of their umbilicals and are usually directed from the surface control point. On those occasions when they need to navigate they can use the same methods used by scuba divers.
Advanced Open Water Diver (AOWD) is a recreational scuba diving certification level provided by several diver training agencies. Agencies offering this level of training under this title include Professional Association of Diving Instructors (PADI), and Scuba Schools International (SSI). Other agencies offer similar training under different titles. Advanced Open Water Diver is one step up from entry level certification as a beginner autonomous scuba diver. A major difference between Autonomous diver equivalent Open Water Diver (OWD) certification and AOWD is that the depth limit is increased from 18 to 30 metres.
Scuba Diving International (SDI) is a Scuba training and certification agency. It is the recreational arm of Technical Diving International, a technical diver training organization.
Master Scuba Diver (MSD) is a scuba diving certification or recognition level offered by several North American diver training agencies, such as the National Association of Underwater Instructors (NAUI), the Professional Association of Diving Instructors (PADI), Scuba Diving International (SDI), and Scuba Schools International (SSI). Other agencies offer similar programs under other names, such as "Elite Diver". Each of these agencies touts their program at this level as the highest, non-leadership program.
Diving equipment, or underwater diving equipment, is equipment used by underwater divers to make diving activities possible, easier, safer and/or more comfortable. This may be equipment primarily intended for this purpose, or equipment intended for other purposes which is found to be suitable for diving use.
A diving instructor is a person who trains, and usually also assesses competence, of underwater divers. This includes freedivers, recreational divers including the subcategory technical divers, and professional divers which includes military, commercial, public safety and scientific divers.
Scuba skills are skills required to dive safely using self-contained underwater breathing apparatus, known as a scuba set. Most of these skills are relevant to both open-circuit scuba and rebreather scuba, and many also apply to surface-supplied diving. Some scuba skills, which are critical to divers' safety, may require more practice than standard recreational training provides to achieve reliable competence.
Autonomous diver is an international minimum standard for entry level recreational scuba diver certification. It describes the minimum requirements for basic training and certification for recreational scuba divers in international standard ISO 24801-2 and the equivalent European Standard EN 14153-2. Various organizations offer training that meets the requirements of the Autonomous Diver standard. A certification which corresponds to Autonomous Diver allows for independent diving with a dive buddy in open water. Most training organizations do not recommend exceeding a depth of 18 or 20 meters at this level of certification. After completion of this certification the training can be extended to a dive leader to ISO 24801-3 or an intermediate not defined by international standards.
Dive leader is the title of an internationally recognised recreational diving certification. The training standard describes the minimum requirements for dive leader training and certification for recreational scuba divers in international standard ISO 24801-3 and the equivalent European Standard EN 14153-3. Various organizations offer training that meets the requirements of the dive leader standard. Some agencies use the title "Dive Leader" for their equivalent certification, but several other titles are also used, "Divemaster" may be the most widespread, but "Dive Supervisor" is also used, and should not be confused with the very different status and responsibilities of a professional diving supervisor. CMAS affiliates certifications which meet the requirements of CMAS 3-star diver should meet the standard by default. The occupation of a dive leader is also known as "dive guide", and is a specialist application of a "tour guide".
Recreational scuba certification levels are the levels of skill represented by recreational scuba certification. Each certification level is associated with a specific training standard published by the certification agency, and a training programme associated with the standard., though in some cases recognition of prior learning can apply. These levels of skill can be categorised in several ways:
