Krk Harbour has anchored maritime trade since Roman galleys carried olive oil and wine north to Aquileia in the first century. The stone quay, rebuilt under Venetian rule in 1480, still shelters fishing boats and passenger ferries beneath the walls of Krk Old Town, where the cathedral's Romanesque bell tower rises seventy metres above the waterline. Today the harbour serves as the departure point for a fleet of glass-bottomed catamarans and traditional wooden gajetas that carry visitors into the Kvarner Gulf, a stretch of the northern Adriatic bounded by the islands of Cres, Lošinj, Rab, and Pag. The geology of the gulf shapes every itinerary. Limestone cliffs drop vertically into water that reaches thirty metres depth within a hundred metres of shore, creating the translucent blue that draws swimmers to Plavnik Island and the secluded coves of Stara Baška. The Blue Cave on the western coast of Krk, accessible only by boat, formed over millennia as wave action dissolved calcium carbonate along a fault line; sunlight refracts through the entrance at specific angles between May and September, illuminating the interior in electric cyan. Golden Beach, a crescent of fine pebble on the uninhabited islet of Plavnik, earned its name from the amber hue of its seabed at shallow depth, visible through six metres of seawater. Modern excursions follow routes established by sponge divers and coral harvesters in the nineteenth century. The five-island circuit — Krk, Plavnik, Cres, Rab, and Goli Otok — covers forty nautical miles and passes the site of a Benedictine monastery abandoned in 1480, now home to a colony of Eleonora's falcons. Evening departures time their return to Krk Harbour for the half-hour window when common bottlenose dolphins hunt mackerel along the thermocline, three kilometres offshore. Operators report sightings on seventy per cent of sunset sailings between June and September. The harbour operates daily from 08:00 to 20:00, with most vessels departing between morning and midday to avoid afternoon southeasterly winds that build after 14:00 in summer months. Mooring space accommodates twelve tour boats simultaneously; early morning slots offer the calmest sea state and the shortest queues at boarding. No entrance fee applies to the port area itself, though each commercial cruise sets its own ticket price and itinerary.