The marine environment is characterised by seabeds with a high morphological variety that favour the presence of species contributing to different habitats, such as the Posidonia oceanica meadows, the pre-coralligenous and coralligenous formations, which play a fundamental role in the variety of the landscape and colours.
On the submerged platform off the Sinis peninsula, parallel to the coast, a long ridge develops connecting Mal di Ventre Island, characterised by large granite blocks and recesses, to the Catalano rock, with deep cliffs of basalt rock and small caves. Rising from the deep escarpment, towards the coast, in the coastal shallows ancient beach lines can be identified, corresponding to the pauses in the rise of sea level which began about eighteen thousand years ago, the most recent of which run parallel to the coast of San Giovanni di Sinis.
P. oceanica meadows in the Marine Protected Area