Filicudi, Sicily, Italy

Grotta del Bue Marino

Grotta del Bue Marino is one of the largest and most famous sea caves of the Aeolian Islands, on the western coast of Filicudi. The cave takes its name from the Mediterranean monk seal (Monachus monachus) that once inhabited Aeolian caves and which is occasionally still reported in the archipelago. The entrance opens at the surface beneath dramatic basalt cliffs and continues underwater into a large chamber with a sandy floor at around 15 metres, with the deeper outer reef descending to about 30 metres. The walls inside and around the cave host encrusting orange Astroides calycularis, yellow Parazoanthus axinellae and red and yellow sponges; yellow Eunicella cavolini fans appear on the outer sections. Resident species include dusky groupers, conger eels, slipper lobsters, octopus, moray eels and scorpionfish, with damselfish swarms and salema schools in the entrance. Visibility regularly exceeds 25 metres. Currents are usually weak. The Aeolian Islands are a UNESCO World Heritage site.