If you dive within the light zone of a cave, the area near the cave entrance where natural light is always visibly, you're cavern diving. If you want to explore secrets hidden in caverns around the world you'll need your PADI Cavern Diver certification.

You need to be an Advanced Open Water Diver or higher and the minimum age is 18 years old.

During your first open water dive you'll practice line handling, reel use and emergency procedures without entering a cavern. But, for your next three dives, you're headed into the cavern, staying within the light zone and 40 metres/130 feet total distance of the surface.

You'll also cover planning, organization, techniques, problems and hazards of cavern diving. Along with special equipment use, such as lights, guidelines, reels and redundant breathing systems. As well as proper body position, buoyancy control, air management and emergency procedures. Cavern diving hazards include silting, line problems, disorientation and emergencies.

There will be at least four dives over two days

• This is not a cave diving course and does not result in a cave diving certification. It does prepare you to enter a cave diving program.