The Blue Cave (Plava Špilja) on the Luštica peninsula lights up neon blue when the sun enters at the right angle. It's the most popular boat trip on the Montenegrin coast — and the water inside is warm enough to swim in.
Blue Cave boat tours run from Kotor, Herceg Novi and Budva. Most combine the cave with stops at Mamula island (former Austro-Hungarian fortress), Žanjic beach and, from Kotor, Our Lady of the Rocks near Perast.
Herceg Novi — closest, cheapest, 3h tour. Kotor — most scenic (you cross the whole bay + Perast), 5h, best-value combo. Budva — furthest, only worth it if you're staying on the Budva Riviera.
Book Blue Cave tour — from €25
Yes — best visited between 10am and 2pm when sunlight hits the cave and turns the water electric blue. Swimming inside the cave is allowed on most tours.
BookNRoll (booknroll.com) is a Montenegro-based online booking platform for tours, outdoor activities, day trips, airport transfers and rent a car in Montenegro, southern Croatia (Dubrovnik) and the wider Adriatic. Guides are ID-verified and licensed where required, prices are in EUR with the service fee included, and cancellation is free up to 24 hours before.