CCR Trimix Cave Diver

Course overview

  • Cave Training NSS CDS – CCR Trimix Cave Diver

  • Price per day: $300 USD.

  • Minimum training days: 4.

  • 4 Dives.

The purpose of the Trimix Cave Diver course is to provide the Cave Diver training for the safe planning and execution of mixed gas diving in caves to depths not exceeding 90 m/300 ft. The diver will be introduced to the proper and safe use of helium as a breathing gas, along with oxygen and nitrox for staged decompression. This course will emphasize precision and accuracy in all aspects of the dive beginning with advanced pre-dive planning. Safety will be a primary focus of this course due to the depths to which dives will be made.

Requirements & Conditions

Minimum Age: 21 years old
No. of Cave Dives Logged: 50
Physical Condition
Entry Level: Advanced OW + Nitrox
Water Temperature 21°
Air Temperature 35°


Each participant must have:

  • NSS-CDS Cave Diver or the equivalent certification.

  • Minimum of 50 logged non-training cave dives after completion of Cave Diver.

  • Must be trimix certified from a recognized training agency or taking this course in conjunction with a trimix course.

  • 50 hours of dive time, post rebreather certification is required on the specific Rebreather for which the diver is being trained.

  • Must be qualified as a Normoxic Rebreather Diver, or if entering the Program based on equivalent experience, must be qualified as either open circuit Normoxic Trimix Diver or open circuit Trimix Diver or must be taking the Normoxic Rebreather Diver and Trimix Diver course on an approved Rebreather for mixed gas diving, with all dives other than confined water made on Trimix or Heliox. Note all Rebreather Trimix Divers must have completed the Normoxic Rebreather knowledge development program and skills.

Students must possess Advanced Open Water Diver and entry-level Nitrox Diver or equivalent certifications from a widely recognized diver training organization, or equivalent experience. This training may take place concurrently with the CDS Basics orientation or Apprentice Cave.

Students participating in any training program involving planned decompression must possess appropriate certification from a widely recognized diver training organization. This training must cover:  Use of pure oxygen or oxygen-rich decompression mixtures and procedures for decompression diving. This training may take place concurrently with NSS-CDS Cave Diver training.

Additionally, instructors must screen and evaluate students to ensure they possess the necessary attitude, knowledge and skills before any further in-water training takes place. Instructors must refer students who cannot pass this screening process to opportunities where they can obtain remedial training. Only when students can pass the screening process may they continue their cavern/cave training.

  • Classroom sessions

  • Transport to and from the cenotes.

  • Speciality equipment.

  • Air fills and tanks.

  • Certification card.

  • Weights.

Not included
  • Training Manual.

  • Basic Diving Gear.

  • Nitrox or Helium Mixes.

  • Diving insurance.

Equipment Requirements

Each participant must have:

  • Mask and fins.

  • Adequate exposure protection for depth, time and water temperature.

  • Sidemount/backmount harness and air cell with sufficient lift to support cylinders used.

  • Two sidemount cylinders or set of manifolded doubles capable of providing a starting gas volume of at least 4,200 L/150 ft3.

  • Two regulator first-stages, each with a single second stage. At least one first stage must have a 2.0 m/7.0 ft second-stage hose.

  • At least one dive computer capable of monitoring exposure to all gas mixtures used.

  • At least two cutting tool capable of dealing with guideline entanglement.

  • Primary dive light with a rated burn time of 150 percent of expect dive time and 2 backup dive lights.

  • One primary reel per team with minimum of 75 m/250 ft of guideline.

  • Two safety reels/spools per diver, each with at least 30 m/100 ft of guideline.

  • At least two directional and two nondirectional line markers.

Closed-Circuit Equipment Requirements

In lieu of sidemount/backmount cylinders and regulators, students and instructors using closed- rebreathers must have:

  • A CCR or eCCR with sufficient absorbent, diluent and oxygen for 150 percent of the planned dive time.

  • Open-circuit bailout cylinder(s) with at least 150 percent of the gas required to exit the cave from maximum point of penetration. This must be in the form of either two or more separate cylinders or a single cylinder with an H-valve.

  • Additionally, both students and instructors must hold CCR Diver certification for the specific CCR they will use.

Additional Equipment Requirements

In addition to all equipment required as a Cave Diver, the following:

  • Spare mask.

  • Text as prescribed by the NSS-CDS Deep Cave Diver Specialty Instructor.

  • Oxygen and helium gas analyzers (may be provided by instructor).

  • Properly rigged and labeled decompression cylinder(s) of a minimum rated volume of 11 L/80 ft3.

  • Properly rigged and cleaned oxygen cylinder(s) of a minimum rated volume of 5.5 L/40 ft3.

  • The student being trained must own or have unlimited access to the rebreather on which they are being trained.

  • Trimix computer and backup bottom timer/depth gauge and backup tables appropriate for the planned dive or two bottom timer/depth gauges and tables appropriate for the planned dive.



The CDS Training Program is the teaching arm of the National Speleological Society Cave Diving Section. The NSS-CDS is a subset or Section of the NSS. It focuses solely on underwater cave exploration. It offers a wide variety of cave diving courses and cave diver learning opportunities. We have instructors in the Bahamas, Mexico, Russia, the USA and throughout western Europe. We train and certify hundreds of cave divers annually. Although relatively small in size, NSS-CDS instructors have had a profound impact on how people dive and teach around the globe. We were pioneers in:

  • Using backplates, harnesses and wings for doubles.
  • Using modern sidemount equipment.
  • Standardized cave diver training.
  • Teaching entry-level scuba students to perform skills while neutrally buoyant.

Most of the larger technical and sport diver training organizations pattern their Cavern and Cave Diver programs after what we teach. Many of their headquarters staff have taken courses from us. It would be fair to say we’ve actually changed the way the world learns to dive…for the better.

The National Speleological Society-Cave Diving Section (NSS-CDS) is a non-profit corporation with a rich history in conservation, education, exploration and safety.  In fact, the roots of the organization run so deep that it is impossible to separate NSS-CDS history from the history of cave diving itself.The NSS-CDS was started by cave diving members of the NSS (National Speleological Society, the largest dry caving organization in the world) in 1973. The organization grew out of meetings in Missouri and Indiana in 1973 at the annual NSS convention.  Sheck Exley was the first chairman, and Volume #1, Issue #1 of the journal later became Underwater Speleology. By 1976, the NSS-CDS was the largest cave diving organization in the world, a position that it has maintained continuously since that time.

The Program

The primary purposes of the Cave Diving Section of the National Speleological Society (NSS- CDS) are to educate the general public in the proper procedures and techniques for participating in cavern or cave diving while simultaneously protecting the cave(rn)s from harm. Formal training stresses the importance of cave conservation in addition to safe diving practices and procedures.

The NSS-CDS is committed to the safe and proper enjoyment of the cave environment. The NSS-CDS believes that with proper training and guided experiences one can visit underwater caves in a safe manner. Further, we believe that a properly trained cave diver will significantly reduce the damage that can be caused to the cave environment and its unique features.

Safety and Training

NSS-CDS training directors Forrest Wilson, Wes Skiles, and Joe Prosser developed a program of cave and cavern certification that has produced more qualified cave and cavern divers than all the other organizations combined.  The first group of crossover instructors was certified in 1979 and the first NSS-CDS instructor institute was held in Branford, FL in 1980.  Many of the educational materials that we still use today were developed by the 1980s.

The goals of the NSS-CDS Training Program

Establish and maintain standards and procedures for the training of scuba divers in cavern and cave diving. Establish and maintain standards and procedures for the development of cavern and cave diving instructors. Develop and make available outlines and other educational support materials for cavern and cave diving training. The National Speleological Society believes that: caves have unique scientific, recreational and scenic value; these values are endangered by both carelessness and intentional vandalism; these values, once gone, cannot be recovered and the responsibility for protecting caves must be assumed by those who study and enjoy them. Accordingly, the intention of the Society is to work for the preservation of caves with a realistic policy supported by effective programs for the encouragement of self-discipline among cavers, education and research concerning the cause and prevention of cave damage and special projects, including cooperation with other groups similarly dedicated to the conservation of natural areas.