The Blue Hole is a vertical chimney running down into the limestone, about 10m in diameter and 25m deep, that connects with the open sea through an underwater arch about 8m down. Understandably, it's a very popular dive site and the snorkelling is also excellent. While diving, the underwater remains of the Azure Window, which collapsed in 2017, can often be seen.

　　Moby Dives and St Andrews Divers Cove, both located in Xlendi, are available for lessons and equipment hire.