Submarine Cave (Mongonisi)
A shallow cave (average depth about 10 m, maximum about 15 m) that runs more than 250 m into the islet of Mongonisi at the southern tip of Paxos. A community listing says a British submarine hid inside during WWII, supplied by Greek partisans. The same source reached 150 m from the entrance and calls the length the main danger.
depth: 0–15 m