Cathedral Cave (Gozo)

A boulder slope rises toward light from somewhere above, and then you're through: a wide, mushroom-shaped opening between 6 and 18m gives way to a dome-shaped air pocket, and you surface inside what looks like a lit swimming pool. The boulders lining the slope up are covered in algae, sea urchins and starfish. Two shore routes reach the site: down roughly 100 steps and across pebbles at Wied il-Għasri, then a surface swim before descending along a wall through 12, 16 and 18m to the boulder field; or, in summer, a ladder at the neighbouring Għar il-Qamħ and a swim west along the cliff. Most centres instead run it as a 30-minute boat ride from Xlendi Bay. Go in the afternoon if you can. The cavern mouth faces west, and afternoon sun turns the water inside a genuine, photographable blue.

Cathedral Cave's dome is big enough that the light effect is the point, not a bonus: divers surface inside a huge air pocket with a ceiling around 15m above the water, lit blue by sunlight bouncing so close to the entrance that it reads as a swimming pool from underneath. Once inside, you can remove your regulator and talk. The acoustics carry, and more than one visitor has tried singing. That sociability is the clearest contrast with Billinghurst Cave, Gozo's other marquee overhead dive: where Billinghurst is long, dark and a genuine test of overhead-environment comfort, Cathedral Cave is bright, wide and built for a slower, more photographic pace.

The dive itself is easier than getting to it. Both shore routes involve a real walk: steps and pebbles at Wied il-Għasri, or a ladder and a cliffside swim in summer at the neighbouring entry point. Pace yourself and save some energy for the surface swim before you descend. A wide-angle setup rewards the light and the diver silhouettes against the dome, and a torch helps pick out the corals and sponges lining the cavern's walls. If shore access looks like too much on the day, the 30-minute boat ride from Xlendi Bay reaches the same site without the walk.