Portugal
Best overall months to dive: Jul–Sep
Portugal's standout diving is offshore, in the mid-Atlantic Azores — a chain of nine volcanic islands roughly 1,500km west of Lisbon, where submerged seamounts like Princess Alice Bank and Condor Bank draw summer aggregations of sicklefin devil rays and blue sharks. Mainland and Berlengas diving exists off the Portuguese coast but is minor by comparison. We're populating the Azores first.