El Río

The boat stops two minutes from La Restinga port, on the eastern face of the lava wall. Follow the channel seaward. The ancient riverbed drops gradually from a shallow entry, the volcanic walls rising on both sides as the depth reaches 20m. The channel stays open above (this is not cave diving), but the scale creates something close to a passage. At the channel's end, turn back and work through the parallel ravines at 5-15m. The rock here is fractured and deep-creviced. Grouper hold the larger cracks; morays take the narrow ones. In the longest caverns, which extend back into the rock well beyond natural light, the Herreña lobsters live. Giant specimens, tucked into gaps at the far ends. You need a guide who knows where to look.

No other site on El Hierro looks like this. The reserve sites on the west side offer calm grouper encounters and gorgonian walls. That is what the island is famous for. El Río is the counterargument. Raw volcanic architecture shaped by a lava river millions of years before the sea arrived. The empty channel reads as absence: no reef growth, no protective structure, just volcanic rock in a form dictated by eruption and gravity. The Herreña lobster (Panulirus echinatus) has claimed the deepest recesses of the caverns, as far from human traffic as the site allows. East coast conditions have to cooperate, and they do not always. Divers who spend a week on El Hierro treat El Río as the prize that requires patience.

Ask your centre about east coast conditions on arrival. If trade winds are active, El Río is off the schedule regardless of your plans; the operator will run reserve sites instead. When conditions are right, the boat ride is two minutes from port. A torch is worth having for the cavern sections — the lobster locations change, and the deepest ones are easy to miss without one. The site is straightforward for Open Water divers staying at 20m. Surge in the enclosed cavern sections is possible if wind has been active recently, even on a day that looks calm at the surface. Dive with a local guide the first time.