Grotta Azzurra

Ustica's Blue Cave is not the famous Capri version — it is a diver's cave, entered underwater and opening into an air-filled chamber where sunlight filters through submerged cracks to cast cobalt and silver light across walls encrusted with sponges, bryozoans, and the delicate pink tubes of serpulid worms. The transition from the sunlit entry to the cave interior is one of the most visually dramatic moments in Mediterranean diving.