Bisevo Blue Cave is a unique karstic formation. The cave is 36 meters long, and it can be accessed only by boat or motorboat, and only in windless weather, when there are no waves. The characteristic blue colour of the cave is a consequence of light refraction. Around noon -on a sunny calm day- rays of the sun pass through an underwater opening of the cave. The whole Bisevo Blue Cave is illuminated with blue light while the objects beneath the water surface turn into silver and pink colours. A number of tourist agencies organize trips to the Bisevo Blue Cave. In the summer excursion boats run daily from Komiza . Many of the tours also include a visit to another spectacular cave not far from here, to the Green Cave - which is bigger in size and emerald-green.