THREE BLUES
Blue Cave vs Green Cave vs Blue Lagoon
Three glowing places on the same day trip, constantly confused — which is which, and where you can actually swim.
See Blue Cave day trips on GetYourGuide ↗The Blue Cave (Biševo)
The famous one: a sea cave on Biševo that glows electric blue around midday, entered by a small local boat through a low opening for a short circuit. You don't swim here, there's a separate cash entrance fee, and it's the most weather-sensitive stop of the day. When people say 'the Blue Cave', this — Modra špilja on Biševo — is what they mean, and it's the stop everything else is timed around.
The Green Cave (Ravnik)
A different sea cave entirely, on the islet of Ravnik, lit green through a hole in its ceiling rather than blue from below. Its entrances are large enough to sail into, and — crucially — you can swim and snorkel here, in clear, green-lit water. If the Blue Cave is the one you look at, the Green Cave is the one you get into. It's often an 'if sea and time allow' stop, so it isn't guaranteed on every day.
The Blue Lagoon (Budikovac)
Not a cave at all: a shallow, sheltered turquoise lagoon between the Budikovac islets, where a pale sandy floor throws the light back blue-green. It's the day's easy swim — warm, calm, clear, often with more than twenty metres of visibility — and there's a small seasonal restaurant on the island. Confusingly, some shorter Split boat trips are branded 'Blue Lagoon' after this spot and never go near the Blue Cave, which is where a lot of booking mistakes begin.
Getting the booking right
The practical upshot: if you want the glowing Blue Cave, book a five-island tour that lists Biševo, and you'll get the Green Cave and the Budikovac lagoon along the way as your swim stops. If you book a 'Blue Lagoon' three-island trip instead, you'll get a lovely swim at Budikovac but no Blue Cave. Read the stop list, look specifically for Biševo, and you'll end up on the right boat.