Cavern diving

Diving the entrance zone of a cave within sight of daylight, on a guideline and within recreational limits; the gateway level below full cave.

Cavern diving is diving in the entrance zone of an underwater cave while staying within sight of natural daylight, the defining line that separates it from cave diving. Typical training limits keep divers inside the light zone, within roughly 60 m (200 ft) of linear distance to the surface, above 21 m (70 ft) of depth, within no-decompression limits, and never through restrictions too tight for two divers side by side.

The point of the limits is that a direct visual reference to the exit always exists, so cavern diving remains within reach of recreational divers with proper training or, in places like the Yucatan cenotes, with certified guides on permanent lines in small groups. Even so, the skills lean toward cave technique: buoyancy that never touches the floor, anti-silt kicks, line awareness, and a light for looking into the dark zones you do not enter.

The Cavern Diver course is both a destination and a gateway: many divers take it purely for the cenotes, while for others it is step one of the full cave path. Respect the daylight rule absolutely, the majority of cave fatalities historically involve divers without cave training passing the sign that marks the end of the cavern zone. The warning signs are blunt for good reason, and every guide will tell you the same.