Tonga
A remote, sparsely developed archipelago of about 50-62 islands, atolls, reefs and shoals in central Tonga, known for uncrowded pinnacle, cave and coral-arch diving and for high underwater visibility.
Ha'apai lies between Vava'u and Tongatapu and comprises around 51-62 islands and reefs, only a minority inhabited. Diving is described as less crowded with better visibility than elsewhere in Tonga, featuring pinnacles, caves, a hydrothermal-vent cave, and the Arch of Ofalanga, the South Pacific's largest known coral arch. Humpback whales are present roughly July to early November. Source: Wikipedia (Ha'apai), tongapocketguide.com.