A fast open-boat run down Boka Bay to swim inside the Blue Cave (Plava Spilja), where sunlight refracts up through the water into an electric glow, with a stop at the islet church of Our Lady of the Rocks. It's the marquee on-water experience of the bay and fits a port-day window easily. Book the early slot to leave buffer before all-aboard.
What to expect
You'll board a speedboat at the Central Park dock and make a fast, open-air run down Boka Bay toward the Blue Cave (Plava Spilja), where you'll slip into the grotto and swim in water that glows with an electric blue refracted light from the sun—the signature moment of the bay. From there, the boat carries you to the islet church of Our Lady of the Rocks for a second stop, then completes the circuit with a pass-by of the submarine base. The full loop runs 3 hours, with the rhythm of transit punctuated by two distinct water stops and the maritime scenery of the bay as your constant backdrop.
The ship sells the identical Blue Cave run for $89-100. This Kotor-based operator does the same route, 3 min from the terminal, for $49 -- you save roughly $40-50 per person and depart on your own schedule.
Good to know
Book the early excursion slot to give yourself a comfortable buffer before all-aboard; the 3-hour duration fits easily into a 6–8-hour port day. The dock is a 5-minute walk from the cruise terminal, so you can time your departure independently without waiting for a ship shuttle. Bring swimwear under your clothes, reef shoes or water sandals, sunscreen, and a towel; safety gear is provided. Book directly with Montenegro Submarine ($49 per person) rather than through the ship ($89–100) to save $40–50 per person while controlling your own schedule.