Vietnam
Best overall months to dive: Mar–Jun
Vietnam is a modest, low-cost dive destination rather than a top-tier one. Diving concentrates in three areas: Con Dao, an offshore national park with the country's best-documented coral; Nha Trang on the central coast, which has the most dive shops and the most reef damage; and Phu Quoc in the Gulf of Thailand, shallow and silty but easy for new divers. Expect moderate visibility, small reef fish and few large animals — divers travelling from the Coral Triangle will find it thin. Con Dao and Nha Trang dive on broadly the same calendar — roughly March to September — while Phu Quoc, over in the Gulf of Thailand, is the outlier at its best from November to April.