TDI Cavern
TDI Training

TDI Cavern Diver

20,000 ฿
4.7 stars, based on 264 reviews.

TDI Cavern Diver at a glance

  • Prerequisites

    1. Minimum age 18, 15 with parental consent.
    2. Provide proof of an SDI Open Water Scuba Diver or equivalent.
    3. Provide proof of a minimum of 25 dives.
    4. Divers must be able to provide proof of experience in order to dive deeper than 18 Meters during this course.

  • #Days

    4

  • Max Depth

    30 meters or the maximum certification depth of the diver, whichever is
    shallower.

  • # Dives

    2 Shallow dives and 4 Cavern dives

20,000 ฿
4.7 stars, based on 264 reviews.
Book online

Step Into the Overhead World: TDI Cavern Diver

Cavern diving is one of the most rewarding steps a diver can take. It opens the door to breathtaking underwater topography, stunning light beams, and crystal-clear visibility, while serving as your official gateway into full cave exploration and technical training.

Whether you want to experience the awe of the overhead environment or master the precise line-handling skills required for advanced diving, the TDI Cavern Diver course is the perfect entry point.

Why Choose Big Blue Tech?

Diving under an overhead ceiling requires a major shift in mindset, specialized safety protocols, and absolute precision. That’s why your choice of instructor matters:

  • Active Overhead Divers: Our instructors don’t just teach cavern diving from a manual—they are active technical and cave divers who regularly explore overhead environments.

  • Comprehensive In-Water Training: Conducted over 4 days, we maximize your time in the water by combining intensive land-based line drills, a dedicated shallow session, and four full cavern training dives.

  • Build Real Experience: We focus heavily on environmental awareness and real-world scenarios, ensuring you leave the course with the confidence to handle reels, lights, and emergency protocols in the overhead enviroment.

Flexible Online Learning

Get the theory out of the way before you even pack your bags. With the TDI eLearning platform, you can complete all of your academics online prior to arriving at Big Blue Tech. Once completed, you will have lifetime access to the digital course materials so you can refresh your cavern safety knowledge at any time.

TDI Cavern Diver gallery

Itinerary

What to Expect: Day 1 of Your Cavern course

Your journey into Caverns starts with a relaxed but structured first day, perfectly balancing essential theory with dry skills and line work.

Morning: Logistics, Coffee & Theory

We kick off the morning by meeting your Big Blue Tech Instructor at our beachfront restaurant. Over a coffee, we’ll take care of the paperwork and review your online academics.

Your instructor will deep-dive into the core principles of technical Cavern diving, including:

  • Equipment Selection & Tuning: Configuration, lines & lights

  • Gas Management: Planning for redundancy and multi-cylinder configurations.

  • Dry skills & Drills: building confidence in yourself and the team around you during line laying and team drills.

Day 2: Precision Line Work & First Shallow Cavern Dives

With the dry skills from day 1 complete, Day 2 is where we transition your skills into the open water. We focus heavily on precise line management and environmental awareness within the cavern zone.

Morning: Cavern Logistics, Reel Prep & Site Planning

Once again you’ll meet your instructor to wrap up the academics. We will ensure you have a thorough understanding of all aspects of cavern diving theory, light signals, and emergency protocols.

Before the lunch break, we will use this time on land to fine-tune your reel handling. You’ll practice running guidelines and making secure tie-offs until the muscle memory is dialed in and ready for the afternoon.

Afternoon: Shallow Dives 1 & 2

After lunch, we head out on the boat for your first two  training dives. By utilizing shallow cavern sites, we maximize your bottom time, giving you plenty of relaxed, low-stress minutes underwater to focus entirely on your technique.

  • Dive 1 (Line Awareness & Propulsion): We focus on executing a clean entry, running a primary reel from open water into the cavern zone, and maintaining a strict guideline. You will practice specialized propulsion techniques (like the frog kick and modified flutter) to ensure we don’t disturb the delicate cavern floor.

  • Dive 2 (Building Competency): This second skills dive is designed to build your confidence inside the overhead zone. Because we are in a shallow, gas-efficient environment, we have the time to comfortably introduce emergency drills along the line—such as touch-contact gas sharing and managing simulated light failures—ensuring your responses become second nature.

Evening: Debrief & Logs

Then it’s back to our bar for a thorough debrief with your instructor, where we’ll review video footage or feedback from the day and log your dives.

Day 3: Mastering the Zone & Graduation

On the final day of your course, everything comes together. You will transition from practicing individual skills to demonstrating true comfort, efficiency, and independence in the overhead environment.

Morning: Emergency Protocols & Advanced Dive Planning

We begin the morning by wrapping up any outstanding academics. Your instructor will expand on advanced emergency management, lost-diver procedures, and lost-line protocols. Working together, you will plan out the gas management and logistics for the final afternoon on the boat.

Afternoon: Shallow Cavern Dives 3 & 4

After lunch, we head out for your final two training dives. Taking advantage of the extended bottom time provided by our shallow cavern sites, you will showcase your mastery of the overhead environment.

Afternoon: Shallow Cavern Dives 1 & 2

After lunch, we head out on the boat for your first two cavern training dives. By utilizing shallow cavern sites, we maximize your bottom time, giving you plenty of relaxed, low-stress minutes underwater to focus entirely on your technique.

  • Dive 1 (Line Awareness & Propulsion): We focus on executing a clean entry, running a primary reel from open water into the cavern zone, and maintaining a strict guideline. You will practice specialized propulsion techniques (like the frog kick and modified flutter) to ensure we don’t disturb the delicate cavern floor.

  • Dive 2 (Building Competency): This second skills dive is designed to build your confidence inside the overhead zone. Because we are in a shallow, gas-efficient environment, we have the time to comfortably introduce emergency drills along the line—such as touch-contact gas sharing and managing simulated light failures—ensuring your responses become second nature.

Evening: Debrief & Logs

Then it’s back to our bar for a thorough debrief with your instructor, where we’ll review video footage or feedback from the day and log your dives.

Day 3: Mastering the Zone & Graduation

On the final day of your course, everything comes together. You will transition from practicing individual skills to truly mastering the cavern environment and demonstrating complete independence underwater.

Morning: Advanced Planning & Emergency Protocols

We begin the morning by wrapping up any outstanding academics. With the basics out of the way, your instructor will expand on advanced emergency management, including lost-diver and lost-line protocols. You will then work on advanced dive planning, ensuring you are fully prepared to plan and execute cavern dives safely and independently.

Afternoon: Shallow Cavern Dives 3 & 4

After lunch, we board the boat for your final two training dives. Capitalizing on the excellent bottom time and low-stress environment of our shallow cavern sites, you will showcase your comfort and competency in the overhead zone.

  • Dive 3 (The Turning Point): This is the dive where everything starts falling into place. Under the watchful eye of your instructor, you will take the lead—managing the team navigation, running the primary reel from open water into the cavern, and executing the dive plan. We will conduct a final skills review and evaluate your precision positioning along the guideline.

  • Dive 4 (The Freedom Dive): Your final course dive is all about relaxing and enjoying the incredible overhead environment. With your buoyancy dialed in, your line awareness sharp, and your lighting techniques perfected, you’ll navigate safely through the cavern zone to experience the pure fun and unique beauty of this discipline. It is the perfect high-note dive to finish the course.

Evening: Debrief & Celebrations

Back on land, your instructor will conduct a comprehensive final debrief to review your success over the last three days. With your certification secured, it’s time to grab a celebratory drink at the bar and watch the sunset with the team!

FAQs

What can I expect to lean?

Your Big Blue Tech Instructor will take you through the following and more:

  • Policy for cavern diving
    • Gas management procedures and management to include dissimilar volumes
    • Psychological considerations of cavern diving
    • Equipment considerations including:
      • Cylinder options
      • Regulator options
      • Buoyancy compensator/harness options
      • Proper weighting
      • Reel options
      • Equipment configurations
    • Communication (light and hand signals)
    • Swimming techniques
      • Body posture/trim
      • Buoyancy control
      • Line following
      • Propulsion (finning) techniques
    • Physiology
      • Breathing techniques
      • Stress management
    • Cavern environment
    • Cavern conservation
    • Problem solving
      • Emergency procedures
      • Equipment failure
      • Silting conditions
    • Accident analysis
    • Cavern diving etiquette
    • Review of dive tables and decompression theory

Does the course certify me to enter the "dark" zone?

No, the TDI Cavern course doe’s not allow a diver to enter the ‘Dark” zone.

Will I be able to dive this certification with Big Blue Tech after the course?

Absolutely, We encourage all of our newly certified students to get back in the water and enjoy their new certifications. With a healthy number of Technical divers on the staff and a dedicated Tech boat, we offer unequaled Tech fun diving opportunities here on Koh Tao.

What's included in the course?

All the required equipment is included in the course:

  • All materials and certification costs on successful completion
  • SIdemount or Twinset (Regs, Harness & Tanks)
  • Fins (Students are required to have boots if they wish to use open healed fins)
  • Exposure suit
  • Back up mask
  • Back up lights
  • Back up bottom timer
  • Primary line and 1 finger spool
  • SMB

What's Not included?

Divers taking a course at this level should have some of their own primary equipment:

  • Mask
  • Dive computer
  • Wrist slate
  • Boots
  • Compass

Equipment can be purchased at Big Blue or rented at low cost during the course.

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