Blue Cave (Plava Špilja), Mamula & Submarine Tunnels Boat Guide

The inner basin of Kotor is a mirror-calm lake framed by vertical karst walls. Cruising northwest through the narrow Verige Strait reveals the three outer basins of Boka Kotorska , Risan, Tivat and Herceg Novi , before opening onto the wild Adriatic Sea along the cliffs of the Luštica Peninsula. A 3-hour speedboat tour from Kotor to the Blue Cave (Plava Špilja) is the single best way to experience the full length of the 28-kilometre fjord in half a day. The route links five distinct stops across calm bay waters and open sea swells. You visit the Baroque island of Our Lady of the Rocks, the secret Cold War Yugoslav submarine tunnels, the circular Austro-Hungarian sea fortress on Mamula Island. It culminates in a 30-minute swim inside the glowing turquoise grotto of Plava Špilja.

01Where Boats Depart in Kotor & Best Departure Windows

Licensed speedboat operators (such as Kotor Boat Tours, Montenegro Submarine & Speedboat Tour, and Lady of the Rocks Boat) depart from the floating pontoons inside Park Slobode (Freedom Park). The piers sit just 120 metres north of the main Sea Gate on the left side of the harbour bridge. Boats carry 8 to 14 passengers beneath a folding sun canopy (bimini top) and depart every 3 hours starting at 09:00, 12:00 and 15:00 from April through October.

Choosing between the three departure slots makes a major difference to both light inside the cave and sea conditions at the mouth of the bay:

• 09:00 Departure (Calmest Sea). The outer Adriatic entrance between Mamula Island and Cape Arza is glass-smooth before the afternoon maestral thermal breeze picks up at 13:00. Morning is therefore the best choice for travellers prone to seasickness or families with children.
• 12:00 Departure (Brightest Electric-Blue Glow). When the sun sits high in the southern sky between 13:00 and 14:30, its rays strike the white sandy seabed outside the submerged arches of Plava Špilja at the optimal angle. Sunlight illuminates the entire cavern interior in neon sapphire blue.
• 15:00 Departure (Golden-Hour Return). Ideal if you climbed San Giovanni Fortress at dawn and want to cruise back through the Verige Strait as late-afternoon light gilds the palaces of Dobrota and Perast.

02Cold War Yugoslav Submarine Tunnels (Potkopi Rose / Rakite)

After your first stop at Our Lady of the Rocks off Perast, the speedboat accelerates across the Tivat basin and through the Kumbor Strait towards the northern shoreline of the wooded Luštica Peninsula. Hidden directly inside the limestone cliff face near the fishing hamlet of Rose are three camouflaged naval caverns , Rakite, Spilice and Rose , blasted out of solid rock by the Yugoslav Navy (JRM) during the 1960s and 1970s under President Josip Broz Tito.

Measuring up to 100 metres long, 10 metres wide and 8 metres high with water depths of 7 to 8 metres. These reinforced concrete-and-rock pens allowed Hero- and Sava-class diesel-electric submarines and torpedo boats to slip underwater inside the mountain without ever being spotted by NATO reconnaissance satellites. Wire-mesh camouflage nets painted with fake boulders and plastic foliage once hung across the portals. Your skipper will steer the speedboat slowly all the way to the dark rear bulkhead of the Rakite or Rose tunnel. Here, side blast-doors lead into abandoned ammunition bunkers and crew escape shafts.

03Mamula Island (Lastavica): 1853 Sea Fortress at the Bay Entrance

Guarding the 1.5-kilometre mouth where the Bay of Kotor meets the open Adriatic Sea stands the perfectly circular islet of Mamula (Lastavica). In 1853, Austro-Hungarian general and Governor of Dalmatia Baron Lazar Mamula erected a formidable round coastal artillery fort covering 90% of the island's rock surface. Its stone walls enclose a central keep, gun casemates and a freshwater moat to prevent naval incursions into Cattaro. Remarkably, the fortress never fired a shot in anger during the 19th century. During both World War I (under Austro-Hungarian rule) and World War II (from May 1942 under Italian occupying forces), the fort became a prison. The island served as a notorious concentration prison camp where over 2,000 local resistance fighters and civilians were interned.

Following a high-profile heritage restoration completed in 2023, the fortress now operates as a luxury boutique resort and memorial museum. Shared 3-hour speedboats pause for 5 to 10 minutes offshore so passengers can photograph its complete 360-degree stone ramparts from the water before rounding Cape Arza into the open sea.

4. Swimming Inside Plava Špilja (Blue Cave): What to Know Before You Dive.

Carved by millennia of Adriatic winter waves into the base of a 30-metre limestone cliff between Zlatna Luka Bay and Cape Mokra Gora on the outer Luštica Peninsula sits Plava Špilja (Blue Cave). It is a 300-square-metre natural sea hall with a vaulted ceiling rising 9 metres above the water and a depth of 3 to 5 metres. Two natural stone arches , a wider southern boat entrance and a lower, submerged light window , allow sunlight to penetrate the water and bounce off the pale limestone floor. The reflection turns every swimmer's hands and goggles into glowing aquamarine.

Speedboats anchor right inside or at the lip of the cavern for a 25-to-30-minute swim stop. Keep three practical tips in mind: first, boats supply foam pool noodles and buoyancy vests if you are not a confident deep-water swimmer. Second, wear your swimsuit under your clothes before boarding at Kotor pier (small open speedboats have no changing cabin). Third, if afternoon southerly swells (jugo) exceed 1.2 metres, skippers cannot safely enter the low rock arch of the Blue Cave. Instead, they substitute a longer swim stop at sheltered Žanjice Beach or Mirišta Cove nearby.

5. Safety, Seasickness Prevention & Private Boat Upgrades.

Before booking a 3-hour Blue Cave speedboat tour at Kotor's Park Slobode pier, keep two practical sea-safety tips in mind. While the first 45 minutes of the cruise through the inner Kotor, Risan, and Tivat basins take place on sheltered, flat fjord water. The final 20-minute leg past Mamula Island rounds Cape Arza into the open Adriatic Sea. If a southerly wind (jugo) or strong afternoon thermal breeze is blowing, open 8-to-12-passenger speedboats will bounce over one-metre swells. Sit in the rear bench seats near the skipper, where the hull pivots with far less vertical motion than the bow. Also choose the 09:00 morning departure if anyone in your group is sensitive to motion.

If you are travelling as a family or group of four to six friends, upgrading to a private 3-to-4-hour skippered speedboat (€180.00 to €250.00 total as of November 2026) transforms the experience. Your skipper can time your arrival at Our Lady of the Rocks and the Blue Cave between the scheduled group waves. You can add a 45-minute stop for grilled fish and cold white wine on the stone quay of Rose fishing village. You can also anchor for an extra swim in the turquoise bay of Žanjice beneath the 15th-century Arza fortress tower.

When comparing speedboat tour kiosks along Kotor's waterfront park, always verify that your ticket price includes the stop at Our Lady of the Rocks, and entry into one of the Luštica submarine tunnels. It should also include a photo pass around Mamula Island, and at least 25 minutes of swimming time at the Blue Cave. Reputable boats carry life jackets in all adult and child sizes, a bimini sun canopy, a stern swim ladder, and bottled drinking water on board.