Secca delle Fumose

The Secca delle Fumose — the Reef of Fumes — is a submerged volcanic seamount rising from 30 metres to just 4 metres below the surface inside the Campi Flegrei caldera, named for the CO2 bubbles that percolate from volcanic vents across its crest and flanks. The effervescent seabed creates a genuinely alien dive experience: streams of silver bubbles rise through curtains of sea grass and sponge-covered rock while Mediterranean wrasse, bream, and damselfish go about their business in this CO2-enriched environment that scientists study as a natural ocean acidification analogue. The unusual chemistry slightly suppresses sea urchin populations, allowing macro algae and gorgonians to grow in unusual densities across the summit plateau.