Bay of Kotor

The Bay of Kotor — Boka Kotorska in Montenegrin — is the southernmost fjord-like inlet in Europe, formed by a drowned river valley that the Adriatic flooded after the last ice age. Four interconnected bays fold into one another: Herceg Novi Bay at the outer entrance, Tivat Bay in the middle section, and the two inner recesses of Risan Bay and Kotor Bay at the head. The Verige Strait, a natural constriction barely 90 metres wide and 10 metres deep between Tivat and Risan bays, is the hydraulic bottleneck that controls water exchange between the outer and inner bays. On spring tides the current through the Verige runs between 0.3 and 0.8 knots — the most significant tidal flow in the entire bay system. The Adriatic itself is the smallest-tidal-range sea in the Mediterranean basin, its exchange with the Atlantic choked by the Otranto Strait at the foot of Italy and Albania. Mean spring range along the outer Montenegrin coast is roughly 0.4 to 0.6 metres. At Kotor, tucked into the innermost reach of the bay, that range attenuates to approximately 0.35 to 0.5 metres on springs. What actually moves water level across the whole bay is meteorology, not astronomy. The sirocco (jugo in local usage), a sustained south-easterly, funnels up the Adriatic from the Libyan coast and piles water against the northern end; during a strong jugo event the water-level rise at Kotor can exceed the entire spring tidal range by a factor of two. The bora — the cold north-easterly that drops off the Dinaric Alps — does the opposite, pushing water out and briefly lowering sea level. Submarine freshwater springs called vrulje rise through the bay floor year-round, supplied by the karst aquifer of the Orjen and Lovćen massifs above; they keep the salinity slightly lower than open Adriatic values at depth, and in summer they create cold upwelling patches visible to snorkellers as shimmering thermoclines in the water column. The bay's enclosure and depth — up to 60 metres near Risan — makes it attractive to superyacht operators and cruise lines throughout the year. The combination of calm water, high limestone mountains, and Venetian architecture concentrated in a single fjord makes Boka Kotorska one of the most photographed stretches of the eastern Adriatic.