Cavern diving offers a glimpse into a mysterious and wonderful underwater world, but no diver should enter a cavern without training. Here are five tips never to forget.

1) Stay in the light. Cavern divers must stay within sight of the entrance; leave the light zone, and you’re cave diving. Cavern divers should keep a distance of no more than 130 feet from the surface.

2) Do the frog kick. A proper frog kick keeps your feet off the ground and directs the kick force behind you, while a standard up-and-down flutter kick can easily stir up sediment.

3) Follow the rule of thirds. Responsible cavern divers always follow the rule of thirds for air consumption — use one-third of your air swimming into the cavern, one-third to make your way back, and keep one-third in reserve as a safety precaution.

4) Fin the line. Cavern-diving courses teach basic line skills, and cavern dives should take place only at sites with permanent route lines in place. Follow the line at all times, but don’t hold onto it. Instead, fin above the line, and swim using it as a reference.

5) Avoid small spaces. Don’t enter confined spaces underwater. Even if smaller side tunnels are within the daylight zone, cavern divers should always stick to the main cavern — and the route line — not only to avoid getting stuck, but also so you don’t damage delicate rock formations.