Marine reserve since 1996. 17-22°C December-February, visibility 30 m. Whale shark August 2024 (9 m). Sunfish August 2025. Submarine volcano Bob. Off-season: smaller groups, less pressure.
El Hierro is recognized as one of the best marine reserves in Spain, but its winter conditions generate debate. The upwellings of the Mar de las Calmas create exceptional biological productivity that attracts whale sharks. Visibility can be spectacular or reduced by plankton. Many divers note that the absence of mass tourism in winter makes the island an almost exclusive destination for experienced divers.
The Mar de las Calmas Marine Reserve, protected since 1996, maintains temperatures between 17 and 22 °C from December to February with visibility of up to 30 meters. In August 2024 a group of divers filmed an approximately 9-meter whale shark close to the coast. After nearly six years without records, in August 2025 the dive centers of La Restinga again documented several basking sharks, confirming that the reserve's recovery is once more attracting large predators. Winter guarantees small groups and less pressure on dive sites.