Monk Seal CaveBiševo Island

The Monk Seal Cave, Medvidina špilja in Croatian, is the Blue Cave's bigger, wilder neighbour. It opens on the south side of Biševo, a few minutes by boat from the Blue Cave and about 23 nautical miles from Hvar Town, and where the Blue Cave is a small chamber you visit in a ticketed boat, the Monk Seal Cave is a vast cavern you simply swim into.

The name is real. The Mediterranean monk seal, one of the rarest mammals in the world, sheltered and raised its pups in this cave until the middle of the last century, and it is still the emblem of Biševo. The seals are gone from the island now, but the cave they chose is easy to understand: a high, wide entrance facing the open sea, a long passage running deep into the rock, and a pebble beach at the far end in the dark where the pups were born.

Swimming in is the experience. From the boat you cross the mouth and the sea floor drops away beneath you, the light turns from turquoise to deep blue and then to black, and your own voice comes back off the walls. Bring a mask: near the entrance the water is clear enough to watch fish move in the shafts of light, and further in the cave keeps a coolness that is welcome after a morning in the sun. There is no fee, no ticket and no queue.

The cave can only be entered in calm seas. The entrance faces south, so any swell from that direction pushes straight into the mouth, and on those days your skipper will show it to you from outside and move on. When it is calm, plan on half an hour: the swim in, a moment of quiet at the back, and the swim out towards a wall of light.

On our Blue Cave & Island Vis tour the Monk Seal Cave is the stop straight after the Blue Cave, before the run round to Stiniva and Komiža, and it is often the part of the day people remember most. Biševo's quiet bay at Porat, with its small sandy beach and a konoba, is a short hop away if you want lunch on the island.