Volcanic arches, caves and lava tubes in water that is reliably flat and 30m clear, with dense fish including groupers…Volcanic arches, caves and lava tubes in water that is reliably flat and 30m clear, with dense fish including groupers, barracuda and rays, plus subtropical strays arriving on the current. The best diving in the Canaries and the least visited island. A marine reserve since 1996 with strict permit caps. El Hierro is a UNESCO Biosphere Reserve and was, before Columbus, the western edge of the known world, with the prime meridian running through it for centuries. A 2011-12 submarine eruption off La Restinga killed the reef locally and it has since recovered, which scientists have documented in unusual detail. Anchorage: La Restinga harbour is small; anchor off in the lee in settled weather. Hazards: Deep water very close inshore; the island shelves fast. Plus