Congresso, Isola dei cavoli

The dive

Il Congresso is a single large granite rock that breaks the surface about 150 m off the western side of Isola dei Cavoli, in the general-reserve waters of the Capo Carbonara marine protected area at Villasimius. It is easy to pick out from the boat: rounded like a panettone, and capped with a permanent layer of gull and cormorant guano from the birds that sit on it. The Air Sub Diving site sheet for the rock describes mooring on the north side, the side that looks across towards Capo Boi, on a slightly sloping granite platform. The seabed here is granite with scattered boulders and Posidonia lower down, and it is level enough that the site is used for course exercises as well as for guided dives.

The route is a clockwise circuit with the rock always on your right. It starts by crossing a channel between big granite blocks at about 12 m. After the first quarter of the circuit the bottom steps away and the boulders get larger, and you pick up granite ridges whose walls carry Eunicella and Paramuricea — the sheet puts a colony of small specimens on the west side at around 18 m. From there the rock opens into sizeable clefts, several of them wide enough to swim through. Slipper lobster (Scyllarides latus) sit in them, and the unlit walls are colonised by orange Parazoanthus axinellae, which is what most people photograph here. You come back up the same way and finish on the platform where the boat is tied.

The marine protected area publishes the site as "Scoglio del congresso" and rates it as first-level, suitable for beginners, with a maximum depth of 28 m and medium-to-high interest for both landscape and fish life. The operator sheet gives a working range of 5 to 25 m and grades the difficulty as low. Occurrence records around the island are ordinary Mediterranean rocky-reef fauna — ornate wrasse, rainbow wrasse, two-banded and white sea bream, painted comber, parrotfish, cardinalfish, brown meagre, octopus and the dotted sea slug Peltodoris atromaculata.

The rock sits in zone B of the AMP, which is the part that matters for planning. In zone B scuba is allowed only as a guided visit run by a diving centre authorised by the park, with prior authorisation from the managing body; diving on your own tanks without a guide is expressly not permitted there. In practice that means booking through one of the Villasimius centres, which is how almost everyone dives it anyway.

• Clockwise circuit of a surfacing granite dome, starting in a boulder channel at 12 m
• Granite ridges with Eunicella and a small Paramuricea colony on the west side at about 18 m
• Wide clefts you can swim through, with slipper lobster (Scyllarides latus) inside
• Semi-dark walls covered in orange Parazoanthus axinellae
• Flat enough near the mooring to be used for course skills

Conditions

Granite bottom with scattered boulders and Posidonia lower down, sheltered from scirocco, exposed to maestrale. The operator sheet calls visibility excellent in all seasons and gives water at about 22 °C in summer and 13 °C in winter. The boat ties on the north side, on a sloping granite platform facing Capo Boi, and the dive is worked within the AMP's 50 m radius of that point.

On current: The operator sheet reports current here as something that turns up after strong maestrale (NW) winds, and notes it can sometimes be strong at the surface even when the dive itself is calm. Otherwise this is a sheltered, undemanding site. The rock is described as ridossato from scirocco, so it is one of the options when the wind is from the south-east.