Portugal
An 8.3 km strait between Faial and Pico islands, designated a Special Conservation Zone, with volcanic boulder fields, calderas and strong tidal currents.
The Faial-Pico Channel is an 8.3 km strait covering roughly 240 km2, designated a Zona Especial de Conservação protecting the loggerhead sea turtle and common bottlenose dolphin. The seabed features boulder fields and 'covas de gigante' erosion calderas 3-8 m in diameter. Strong tidal flow creates drift dives with dense schools of fish and pelagics such as barracuda and tuna. Source: Wikipedia (Faial-Pico Channel), Ecologic Institute.