La cueva del diablo

Most boats drop divers on the buoy at the foot of the cantil, the rocky cliff line that defines this stretch of reserve coast. The cliff falls past five metres to a sand-and-stone shelf at 12 to 15 metres, with the cavern mouth visible to one side and a small stone arch on the sand at 5m. Inside the chamber the register changes. The collapsed ceiling forms two wide openings, and after midday these become directional shafts cutting through the vault to the sandy floor at around eight metres. The cavern is large and well-lit enough that natural light reaches every corner; centres run it as an Open Water site, not as an overhead-environment dive. Moray eels work the wall crevices, both lobster species shelter in the deeper recesses where a torch helps, and porcupinefish drift near the entrance. Outside, the sandy exterior stays shallow to 15 metres, with octopus and the occasional grouper on the scattered stone, and the stone arch at 5m doubles as a final feature on the way back to the buoy. No current pushes you through. The dive rewards stillness over distance.

Three things set this site apart inside the reserve roster. It is the largest cavern Mar de las Calmas has, and divers consistently land on the same image to describe it - a church vault. The two skylights in the partially collapsed ceiling are the geometric signature, and the post-midday sun turns them into directional shafts of light rather than diffuse glow. And the cavern is not only an underwater feature: it continues above the waterline as a known cliff cave, and at the right tide the surface entrance can be reached by swimming or by small boat. One 2018 first-person account describes the spatial sensation inside as flying in three dimensions, a great room with the fallen-roof ray of light. That low-stress, photogenic register is the site's role on the El Hierro buoy list, distinct from El Bajón's deep pinnacles, El Saltu's lava-tube circuit, or El Desierto's garden eels.

Buoyancy matters more here than at any open-water site. The sandy floor silts easily and ceiling contact dislodges sediment that clouds the chamber for everyone behind. Schedule the dive for the afternoon to catch the strongest skylight effects, and bring a torch for the deeper recesses where the lobsters hide; navigation inside relies on natural light. The boat ride from La Restinga is around fifteen minutes. Shore entry is technically possible but involves a difficult walk with equipment and is not recommended. All diving in the reserve runs through licensed centres, with a maximum of twelve divers per buoy and no anchoring or drift diving, so booking with one of the four La Restinga operators is the only way in. Multi-day visitors waiting for an El Bajón weather window often pair this site with El Saltu or La Herradura on the same outing for variety without raising the difficulty.