The Capo Carbonara Marine Protected Area, established in 1998, encompasses 86 square kilometers of coastline where granite headlands plunge into waters holding Posidonia meadows older than most European cities. Villasimius sits at the eastern threshold of this reserve, a fishing village turned gateway to a coastline the Italian Ministry of Environment ranks among the Mediterranean's twelve most biodiverse. The protected zone extends from Punta Molentis in the north to Capo Boi in the south, wrapping around the uninhabited island of Serpentara and its 19th-century lighthouse, still operational under automated control since 1989. The reserve's establishment followed decades of unregulated anchoring and trawling that stripped seagrass beds across southern Sardinia. Today, Zone A waters—covering roughly 30% of the protected area—prohibit all motorized traffic except authorized research vessels and permitted tour operators who must maintain speed limits below five knots and anchor only in designated sandy corridors. The recovery has been measurable: grouper populations increased 240% between 2002 and 2019, and loggerhead turtles now nest on three beaches within the reserve each summer, a behavior absent from this coastline for most of the 20th century. Boat access operates under a quota system managed by the Consorzio di Gestione, the entity that oversees all commercial marine traffic. Operators receive seasonal permits capped at 18 vessels per day during July and August, with launches concentrated at Porto Turistico di Villasimius, a marina built in 2004 with 300 berths and fueling facilities compliant with EU marine pollution standards. The quota system, controversial when introduced in 2011, has kept visitor pressure below the threshold identified in the reserve's 2015 carrying-capacity study, which set a maximum of 450 daily visitors across all tour types to prevent anchor damage to seagrass beds. Most operators follow a southeastern route: departure from the marina, a slow pass along the granite cliffs of Capo Carbonara where peregrine falcons nest in spring, then anchoring at Cala Caterina or Punta Molentis for snorkeling above Posidonia beds that glow amber-green in midday sun. Serpentara Island lies 1.8 nautical miles offshore, accessible only to permitted boats; its western cove offers the reserve's clearest water, with visibility often exceeding 25 meters in settled weather. The return leg typically includes a drift past Isola dei Cavoli, a second uninhabited islet where Eleonora's falcons migrate each autumn, and where a Spanish watchtower built in 1591 still stands, its limestone blocks stained orange by centuries of lichen. Weather shapes the season: the maestrale wind, blowing from the northwest, can pin boats to harbor for days in May and October. Most skippers favor June and September, when the sea flattens and water temperature holds between 22 and 24 degrees Celsius, warm enough for extended snorkeling without a wetsuit. August brings the calmest conditions but also the highest demand, and advance booking becomes necessary as daily permits fill weeks ahead.