Central Vietnam

Central Vietnam wraps the long South China Sea coast between the Gulf of Tonkin in the north and the Mekong Delta in the south, with Da Nang the working capital of the central region and Hoi An, Nha Trang, and Quy Nhon strung down the coast as historic port towns and modern beach corridors. The tide here is a small predominantly diurnal signal characteristic of the Gulf of Tonkin and the central Vietnamese coast. Mean range at the Da Nang Tien Sa harbour gauge is about 0.9 metres, climbing past 1.4 on the largest spring tides and dropping near 0.4 on neaps. Most days produce one clear high and one clear low rather than the two-and-two semidiurnal pattern, with a smaller secondary excursion at certain lunar phases. The defining seasonal force is the monsoon split. From October through January the north-east monsoon drives swell, rain, and the seasonal flooding events that periodically inundate the Han River and Thu Bon River deltas. From May through August the south-west monsoon brings calm hot weather and the working surf season at My Khe and Non Nuoc when the offshore wind cleans up the shore-break. The American military rebranded My Khe as China Beach during the Vietnam War, ran an in-country R-and-R station there from 1965 through 1973, and seeded the post-war Vietnamese surf scene that returned through the 1990s. The Marble Mountains south of Da Nang hold a network of Hindu and Buddhist sanctuaries cut into limestone karst that the Cham civilisation founded a millennium before the war. Coracle fishermen working the inshore grounds, the bridge spans across the Han River, and the Hoi An ancient town an hour south where the Thu Bon meets the sea all read different parts of the working calendar. The Vietnam Hydrographic Department publishes the authoritative tide tables.