The Blue Grotto is a sea cave on the coast of the island of Capri, southern Italy. Sunlight passing through an underwater cavity and shining through the seawater creates a blue reflection that illuminates the cavern. The cave extends some 50 metres into the cliff at the surface, and is about 150 metres (490 ft) deep, with a sandy bottom.
The cave is 60 metres long and 25 metres wide. The entry is two metres wide and roughly one metre high at low tide, making safe access possible only when tides are low and the sea is calm. To enter the grotto, visitors must lie flat on the bottom of a small four-person rowboat. The oarsman then uses a metal chain attached to the cave walls to guide the boat inside the grotto.
In 2011 a visitor suffered a life altering injury when his neck was broken while entering the cave. The Cooperativa Battellieri Grotta Azzurra initially denied liability but settled a damages claim. It was concluded that the boatmen had continued entering the cave when the sea conditions were inappropriate. Swimming in the grotto is forbidden.