Split's snorkeling corridors radiate from a coastline that has served mariners for twenty-three centuries, yet the underwater clarity along the central Dalmatian archipelago remains its most guarded asset. Krknjaši Bay on Drvenik Veli records visibility exceeding thirty metres during calm mornings, a consequence of minimal riverine sediment and the Adriatic's steep shelf geometry. The Blue Lagoon earned its colloquial name not from tour marketing but from fishermen who noted the turquoise gradient created by white limestone sand reflecting midday sun through shallow water columns. Split Croatia snorkeling tour operators concentrate departures between April and October, when sea temperatures climb from sixteen to twenty-five degrees Celsius and the maestral wind patterns stabilise. The Pakleni Islands, Brač's southern coves, and the rocky perimeter of Šolta present distinct benthic ecosystems: Posidonia meadows shelter juvenile fish, while limestone overhangs host octopus and damselfish. These sites lie within the eleven-thousand-square-kilometre expanse of the Adriatic that Croatia manages under its maritime jurisdiction, a zone where commercial trawling restrictions have allowed reef structures to recover since the early two-thousands. The modern iteration of Adriatic snorkeling evolved alongside Split's tourism infrastructure, which expanded rapidly after the country's 2013 accession to the European Union. Speedboat charters replaced the slower konoba-run excursions that once ferried locals to secluded beaches. Today's six-to-eight-hour circuits bundle swimming stops with cultural anchors—Hvar's Renaissance architecture, the stone hamlets of Vis—but the underwater intervals anchor the experience. Equipment quality varies: premium operators stock prescription masks and wetsuit options for shoulder-season departures. Conservation protocols remain informal. Krknjaši Bay carries no entrance fee, and while tour guides brief passengers on reef etiquette, enforcement depends on operator discretion. The absence of mooring buoys at popular sites means anchor damage persists in high-traffic zones. Environmental groups have documented coral abrasion along the Blue Lagoon's northeastern edge, where shallow draft vessels concentrate during peak summer weeks. The Adriatic's relative oligotrophy—low nutrient levels that sustain its clarity—also renders its ecosystems fragile. Recovery from physical disturbance proceeds slowly in waters this transparent.