Grotta dei Fantasmi

The dive

The Grotta dei Fantasmi opens in the side wall of the Punta Giglio promontory, on the east flank of the limestone massif north-west of Alghero, at around 5 to 6 m. Marco Busdraghi found it on a night dive in the summer of 1994 while running the diving at the Hotel Baia di Conte, and named it for the perforated, blindingly white limestone inside, which reads like sheets thrown over ghosts. It is a forced-conduit cave: fresh water dissolved the rock and then pressure flow tore the resulting decoration apart. What is left is alabaster in every corner — floors, ceilings, layered cascades — with broken stalactites and collapsed structures lying among dunes of sand and clay mud.

Busdraghi's own site sheet gives the cave two entrances, a minimum depth of 0 m and a maximum of 8 m, and describes it as very articulated: a further three openings inside, and a circular route with a surfacing pause in an air pocket where alabaster cascades and stalactites catch the torch beam. The Capo Galera Diving Center describes the same dive from the water: a small atrium leads into a passage and then a flooded chamber with two white rock formations standing against an absolutely black background, like a door into the mountain, then a fairly wide tunnel of about thirty metres that turns back on itself and returns to the chamber, plus a second, smaller tunnel. Daylight never reaches any of it. Italian caving sources put maximum penetration at roughly 70 m.

Two things follow from that, and they matter more than the depth. First, there is very little life inside — Busdraghi is explicit that the near-total absence of light leaves the cave almost empty, and the fauna a diver sees here is on the outside wall rather than in the rooms. Occurrence records for this stretch of the Punta Giglio coast cover the usual semi-dark hard-bottom cast: red banded cleaner shrimp (Stenopus spinosus), common prawn, spiny squat lobster, leopard-spotted goby, conger, and the sponges and dotted sea slugs that go with them. Second, the silt. Both the discoverer and Capo Galera warn about it: there is a great deal of suspension sitting on the floor waiting to be lifted, and a careless fin stroke ends the visibility for everyone behind you.

The cave is site 3 on the marine protected area's list of submerged caves that may be visited, in zone B of the AMP Capo Caccia — Isola Piana. The 2025 disciplinare attuativo caps it at 6 divers per dive and 3 dives per day, requires prior authorisation and an authorised diving centre, allows daytime only, and confines the dive to a 50 m radius from the mooring buoy. It also singles this cave out: a guide needs at least a first-level cave specialty (Cavern Diver or equivalent), and for anyone diving it without a centre's guide the requirement is a second-level specialty — Cave Diver or equivalent. Fantasmi is the only cave in the entire protected area that carries that requirement.

• Two white rock formations standing against a black background like a door into the mountain
• Alabaster cascades, floors and ceilings, with collapsed stalactites lying in sand and clay
• A surfacing pause in an air pocket inside the cave
• A roughly 30 m tunnel that loops back to the chamber, plus a smaller second tunnel
• Shallow enough that the dive is limited by training and gas planning, not by depth

Conditions

Enclosed, dark and still. The rock is exceptionally white and throws the torchlight back, which the discoverer notes is part of the effect; the water inside is described as very clear until the floor is disturbed. Sand and clay mud cover the bottom of the rooms. Because the cave is at 5 to 8 m the dive is long on gas and short on decompression pressure — the constraint is training, light and silt discipline.

On current: Depth and current are not what make this dive serious — the cave is shallow and enclosed. The variable that actually governs the dive is the silt on the floor and the fact that daylight does not reach the rooms, so the entire route is run on torchlight and on the guide's line of travel.