Cinco Ribeiras

Entry is from the coast, down a ladder or with a giant stride off a concrete platform into a natural shallow pool, according to the fullest description of how divers actually get in the water. A short swim along an underwater wall passes the boiler of the Union, a steamship that went down here on 26 June 1911, before the wall opens into the mouth of a lava-tube cave at around 14 metres. Inside, spacious galleries connect through corridors and narrower passages, with rolled-stone, boulder and sand-clearing floors, down to a maximum of 16 metres; divers can push on to an exit at the far end of the system or turn back the way they came. Divers who skip the cave stay in the shallower lava-wall-and-sand terrain near the entry, where the wreck boiler and the surrounding rock keep the dive going without ever entering an overhead space.

Cinco Ribeiras pairs a documented shipwreck at the entry with the volcanic cave beyond it: galleries formed by flows from the Santa Barbara volcanic complex, not built or blasted. The site also carries its own protection, TER18, a Marine Resource Management Area of about three hectares covering the submerged cave and registered on its own, not folded into a wider zone.1 Divers who stop at the boiler and the surrounding wall-and-sand terrain still get a full dive; those ready for the confined sections beyond push on into the galleries, where the daylight fades within a few fin kicks of the cave mouth.

The cave's interconnected galleries and corridors are a genuine overhead environment, with confined sections in places; keep a direct route back to open water and reserve the full route for AOW-level comfort. A dive light earns its keep once the tunnel narrows and the galleries lose the surface light.