Specialist areas: sidemount, rebreathers, scooters, surveying and scientific diving

Reading is no substitute for supervised training. The courses described here sit at or beyond full cave level, and every agency reviewed requires substantial supervised and independent cave experience before them. Nothing below is a procedure.

Sidemount

Sidemount means carrying cylinders along the diver's sides instead of on the back. In cave training it appears in two ways.

First, as a configuration for ordinary cave courses. The NSS-CDS accepts two sidemount cylinders or manifolded doubles for Apprentice Cave, and asks for technical sidemount training or equivalent experience beforehand ^[1]. IANTD accepts sidemount as one of the configurations for its Cavern / Limited Mine course ^[2]. SSI's Cave Diving can be taken in sidemount, twinset or on a rebreather ^[3]. GUE defines its own sidemount configuration in its standards ^[4].

Second, as a speciality for tight cave. The NSS-CDS Advanced Sidemount Diver course, open to full cave divers with at least 50 non-training cave dives after certification, addresses passages so narrow that one or both cylinders must be removed, the risk of becoming unable to back out of a passage (which the NSS-CDS calls a ratchet effect), and a teammate becoming stuck in a long single-file restriction ^[5]. When the NSS-CDS restructured its programme around 2019-2020, the rise of sidemount was one of the reasons given ^[6].

Narrow passages remain outside most entry-level cave cards. TDI excludes areas too small for two divers side by side at cavern level ^[7], and GUE Cave 1 does not allow passages that force single-file travel for any prolonged distance ^[4].

Rebreathers

A closed-circuit rebreather (CCR) recycles exhaled gas, which greatly extends how long a gas supply lasts. Cave rebreather courses therefore focus on what happens if the unit fails far from the entrance, and on carrying enough open-circuit bailout gas to exit.

• The NSS-CDS describes CCR Cave Diver as the closed-circuit equivalent of Apprentice and Cave combined. It requires 25 dives and 35 hours on the same rebreather beforehand and sets bailout at no less than 150 percent of the gas needed to exit from the furthest point ^[8].
• GUE's CCR Cave requires Cave 2, its CCR Technical Diver Level 1 and 50 non-training rebreather dives in that configuration. Training is limited to 30 m and 30 minutes of decompression, with bailout sufficient to exit from maximum penetration at all times ^[9].
• IANTD's CCR Cave Diver requires its rebreather introductory cave course and 50 rebreather dives, or 100 rebreather dives without that course, with a 40 m maximum depth ^[10].
• UTD requires Cave 2 plus its Cave Stage course before CCR Cave ^[11].

The recurring theme is unit-specific experience: each agency wants many dives on the exact rebreather before it is taken into a cave.

Scooters (DPVs)

Diver propulsion vehicles, often called scooters, let a team travel much further than swimming would allow. Agencies treat that extra distance as the central hazard: if a scooter fails, the team has to be able to get out without it.

• TDI DPV Cave Diver requires Full Cave and 25 non-training full cave dives. Its published graduate limits include turning a single-scooter dive with at least twice the gas needed to swim out, and 39 m maximum depth ^[12].
• The NSS-CDS DPV Cave Diver requires 50 non-training cave dives after Cave Diver and describes stage training as close to essential. It notes that some sites ban scooters and warns that even twice the starting gas volume in reserve may not be enough ^[13].
• GUE DPV Cave requires Cave 2, its DPV 1 course and 50 non-training Cave 2 dives, keeps in-water ratios at two students per instructor, and covers trigger-time planning, towing and runaway scooters ^[14].
• The CDAA includes DPV use in its Advanced Cave theory ^[15].

Survey and cartography

Cave maps are made by divers who measure distances, directions and depths along a line and sketch the passage around it. Survey courses teach the methods, the division of work within a team, and the handling of data afterwards.

• TDI Cave Surveying Diver covers compass use, sketching, survey stations, vertical and radial surveys, data verification and different map types, and includes landowner relations. Graduates are limited to the one-third rule, 39 m and 6 m minimum starting visibility ^[16].
• NSS-CDS Cave Surveying covers the history of survey standards, the phases of a survey project, accuracy standards, symbology, cartography and copyright and publication; the section also lists a separate Cartography course ^[17].
• GUE Underwater Cave Survey requires Cave 2 and 25 further Cave 2 dives and aims to prepare divers to assist coordinated cave projects. Its standard requires all survey tasks to be finished before penetration gas limits are reached ^[18].

Survey data are often owned by the projects or landowners involved, which is why publication and copyright appear in the NSS-CDS syllabus ^[17].

Scientific diving

Researchers who dive in caves usually work under an institutional scientific diving programme rather than as recreational divers. In the United States, the American Academy of Underwater Sciences publishes consensus standards, and its 2025 manual has a section on scientific cave and cavern diving ^[19]. Under it, no planned operations in caverns or caves may take place without approval from the organisation's Diving Control Board or its designee; cave authorisation follows cavern authorisation; cave training includes at least twelve cave dives, preferably at four sites with differing conditions; and training must be delivered by agencies or instructors the board approves ^[19]. Where a cave project also uses staged decompression, rebreathers or mixed gas, the requirements for each of those apply as well ^[19].

Stage cylinders and decompression

Several agencies treat extra cylinders and decompression as their own steps. GUE introduces bottom and decompression stages at Cave 2 ^[20]. UTD adds stages through Cave Stage and decompression through Cave 3, after a Cave 2 level that stays within no-decompression limits ^[11]. The CDAA's Advanced Cave covers staged diving at sites with unlimited penetration distance ^[15]. TDI's Full Cave requires separate decompression training when decompression dives are included ^[21].

The common thread

Every speciality here assumes full cave certification, or close to it, and a minimum number of logged non-training cave dives. Specialities extend range or capability; they do not replace the core skills taught earlier, and each brings its own failure modes that are learned in the water with an instructor.