Cefalù's shoreline sits where the Madonie massif meets the Tyrrhenian Sea, a geological collision that carved a fifteen-kilometer stretch of limestone headlands, underwater caves, and sheltered coves between Capo Plaia and Capo Cefalù. The rock itself is calcarenite, a porous sedimentary formation deposited during the Miocene, and its erosion over seven million years created the natural arches and submerged ledges that today anchor kelp forests and schools of Mediterranean damselfish. Water clarity here averages twelve to eighteen meters between May and October, a function of minimal riverine input and the offshore current that sweeps west from Messina. Snorkeling in Cefalù Sicily developed as a recreational activity in the 1980s, when local fishermen began converting wooden lampara boats—originally built for nighttime anchovy fishing—into passenger vessels. Today the fleet numbers forty-three licensed operators, most departing from the old harbor beneath La Rocca, the 270-meter dolomite promontory that towers over the medieval quarter. The coastal snorkeling tour follows a predictable arc: departure at nine or ten, a twenty-minute sail west to the Presidiana caves, forty minutes in the water, then a slow drift back past the Norman cathedral's twin façades while prosecco and arancini circulate on deck. Equipment is standardized—Cressi masks, Mares fins, three-millimeter shorty wetsuits for anyone arriving between November and April. The underwater topography rewards patience. Visibility drops sharply below five meters, where the rock transitions from sun-bleached white to a tannin-stained ochre, and most marine activity concentrates in that littoral band. Salema porgy move in tight formations along the kelp margins. Octopus vulgaris occupies the cave mouths, identifiable by the midden of crab carapaces at the threshold. The star attractions are the posidonia meadows—seagrass beds that stretch unbroken for two kilometers west of the harbor, their rhizomes centuries old, their fronds sheltering juvenile sea bream and cuttlefish. These meadows are protected under Natura 2000 designation, which prohibits anchoring within the zone and limits snorkeling groups to fifteen participants per guide. Cefalù's tourism economy pivoted decisively toward water-based activity after 2019, when overtourism in the historic center prompted the municipality to cap daily visitors at twelve thousand. Snorkeling tours now represent twenty-two percent of all paid excursions originating in the town, second only to Madonie hiking. The boats themselves remain low-tech: no sonar, no GPS fish-finding, no underwater scooters. Departure times align with the tidal slack, and the route never strays beyond sight of La Rocca.