The Split archipelago comprises more than 1,200 karst islands, of which fewer than seventy are inhabited year-round. Croatian cartographers in the 1970s catalogued each fragment of limestone larger than ten square metres, and the resulting maritime cadastre remains the Adriatic's most detailed chart of submerged reefs and navigable channels. Modern island-hopping routes from Split concentrate on a western arc that includes Šolta, Brač, Hvar, Vis, and the islets between them—a corridor defined less by distance than by the depth of the Adriatic trench and the prevailing summer maestral wind. The archipelago's geology is a legacy of Cretaceous-era tectonic uplift and subsequent glacial-period sea-level changes. When the Mediterranean basin refilled twelve thousand years ago, river valleys became fjord-like channels and ridgelines became island chains. The Blue Cave on Biševo exemplifies this process: a sea-level grotto whose ceiling aperture refracts morning sunlight into a cerulean glow visible only between May and September, when the sun's angle permits horizontal penetration of the water column. Vis, the archipelago's westernmost inhabited island, served as a Yugoslav naval base until 1989, and the resulting four-decade closure preserved both its pre-industrial fishing villages and its underwater archaeological sites, including Roman amphorae fields at depths accessible to snorkelers. Split boat trips to islands depart daily from Obala kneza Domagoja, the waterfront promenade east of Diocletian's Palace, where Jadrolinija's terminal anchors the commercial ferry network. Speedboat operators occupy adjacent berths, their fibreglass hulls built for the twenty-to-thirty-knot crossings that reduce travel time to Hvar Town from two hours by ferry to forty minutes by rigid inflatable. The routes vary by operator and season: five-island circuits covering Vis, the Blue Cave, Stiniva Cove, Budikovac's Blue Lagoon, and Hvar typically span ten hours; three-island versions omit Vis and focus on the Šolta-Brač-Hvar triangle. Swimming stops are calibrated to tidal windows and anchorage regulations, and captains adjust itineraries in real time when the bora wind exceeds fifteen knots. The archipelago sustains a fishing economy that predates Diocletian's retirement to Split in 305 CE, and contemporary island populations remain tied to sardine, anchovy, and octopus yields despite the post-1990s growth of nautical tourism. Most island boat trips conclude with a Hvar Town stop, where the Venetian-era arsenal and the Renaissance loggia frame a harbour that has serviced merchant galleys, Austro-Hungarian steamships, and modern catamarans across seven centuries.