Life under the sea
The initial undersea section displays an attractive uniform green, split up into separate tracts by large, rounded, yellow-gold sponges, where other small plants also vegetate. At this depth, there are only a few fish to be seen.
On the grasslands of Mediterranean tapeweed
When the seabed reaches 4-5 metres in depth, a 1.5 metre high dark green line marks the beginning of the grasslands of Mediterranean tapeweed, which are at their most lush at around 10 metres deep. All of a sudden, the dynamism of marine life increases, and there are many more species of fish to be found: chromis chromis, bream, cuckoo wrasse, the camouflaged broad-nosed pipefish (which can easily be mistaken for a leaf of tapeweed), banks of sarpa salpa, large groupers, blotched picarel, Marida picarel and cuttlefish. These waters play host to a large number of urchins, with their delicious gonads.
This is also home to the fan shell (Pinna nobilis), which is the largest bivalve in European waters and which secretes a byssus that was once used for the production of fabrics and was known as “sea silk”.
Off the coast, surrounded by anemones and shoals of fish
In the tracts closest to the coast, the grasslands of Mediterranean tapeweed appear irregular, interrupted by sandy clearings.
This section of the sea plays host to the flat, wide-eyed flounder and the brightly coloured greater weever, as well as stargazer, lizardfish, red mullet, reef mullet, striped seabream, flying gurnard and pearly razorfish.
The fish are present in great numbers, with myriad youthful shapes and small sizes, thus confirming the nursery function of the bay.
Sea anemones are frequently found in the breaks between rocks – they are fished intensely as they are very popular when fried.
Close to the surface, it is easy to catch a glimpse of needle fish and small mullet flashing past. When the sea is rough, gilthead, large white bream and predators such as sea bass appear out of the blue.
The underwater caves – the habitat of crayfish and lobsters
As you proceed gradually towards the outlet of the bay, the coast becomes higher.
The cliffs continue for several metres below the surface and you come across the first underwater caves, which formed above the water around 70 million years ago and are now below the surface.
The first section plays host to numerous colonies of red algae, along with sponges of various colours, false coral snake and red sea squirt.
Proceeding towards the interior of the caves, you come across numerous Parazoanthus axinellae and myriad other species, thus confirming the extraordinary biodiversity of these caves.
On leaving the bay of Porto Conte, you come to the submerged caves of Capo Caccia, which are extremely imposing and stretch to several dozen metres in width. Having passed beyond the facies that are covered in red coral, the deeper you advance into the caves the more the rock appears naked.
This is the realm of large shellfish such as lobster, crayfish, slipper lobster, squat lobster, shore crab, dromia personata crab and prawn. Fish species present in large numbers here include sea bass, European conger, certain species of grouper and pout whiting.
By now, the sunlight has almost entirely disappeared and sub-aqua divers must rely exclusively on electric torches. The limestone formations include stalactites.
The base of the cliffs
Externally, along the cliffs of Capo Caccia and Punta Giglio, the seabed slopes down rapidly between large masses where you encounter predators such as dentex, sea bass and greater amberjack, which glide past rapidly spreading fear amongst the smaller fish. Up above, the elongated silhouettes of barracudeas flash by.
On the walls of the masses you will see madrepore and branches of red coral.
Heading towards the area in front of the Capo Caccia promontory, more than 40 metres down, you will witness another breathtaking sight.
We are in the realm of great red gorgonian coral and black coral with yellow polyps.
This marks the start of a fascinating world – the world of coral biocoenosis and of the clastic coastal seabed.
A hotspot for sub-aqua divers, the cave is also exceptionally rich in marine life: from fish such as grouper and sea bass, through crayfish and lobster, all the way to sponges and moss animals.