Overview
The light comes from below: the underwater arch is much larger than the visible entrance, so what reaches the water inside is filtered of red and arrives as blue from beneath. The Romans knew it and used it as a nymphaeum, with statues set around the walls; several were recovered from the floor and are in Anacapri. The cave closes whenever the swell is up or the tide is high, which is often, and no ticket guarantees entry.
Highlights
Go early in the morning, when the sea is calmest and the queue of boats is shortest — by midday the wait can be an hour on the water. The visit inside lasts about five minutes, which is the honest expectation to arrive with. There are two fares, one for the boat from Marina Grande and one for the rowing boat at the entrance, and the rowers expect a tip.