The Blue Hole is a natural shaft in the limestone at Dwejra, on the west coast of Gozo.
It is about ten metres across and open to the sky.
At the bottom, around fifteen metres down, an arch leads out through the cliff into open water.
Divers drop into the shaft, swim out through the arch and turn along the wall outside.
What you see
The arch starts at about six metres and runs down past fifteen.
Swimming out through it with the light behind you is the photograph everybody takes.
Outside, the wall drops away to around sixty metres. Most recreational dives turn at thirty or less and work back along it.
There is a cave to the left of the arch, shallow enough to look into without a light.
The boulders from the collapsed Azure Window lie scattered on the seabed nearby. The window fell in a storm in March 2017.
Expect groupers, bream, octopus in the cracks and the occasional barracuda out on the wall.
What you need
Open Water is enough if you stay above eighteen metres, which covers the shaft and the arch.
Working along the wall wants Advanced, because the bottom is well past recreational limits and it is easy to drift deeper than planned.
It is a shore dive and the entry is the hard part.
You cross a stretch of rough, sharp coralline limestone in full kit, then take steps carved down into the shaft.
Boots you can walk in matter more here than on any other Maltese site.
When not to go
Dwejra is exposed to the west and northwest. When either is blowing the site is closed.
That call is made on the morning, not the day before. There is more on the four winds and what each one does.
In summer it is busy from early. Go first thing or wait your turn at the steps.
Dive centres in Gozo run it daily and will tell you honestly if the swell is wrong.
If you are not diving
You can snorkel the shaft and see the top of the arch from the surface.
The Inland Sea is a few minutes’ walk away, and the boats that run out through its tunnel leave from there.
The whole Dwejra area is worth an hour on foot even with no kit at all.
