Vietnam extends along 3,260 kilometers of coastline facing the South China Sea, which Vietnamese maps designate as Biển Đông, the East Sea. This measurement runs from the land border with China at Móng Cái in the north to the terminus at Hà Tiên near Cambodia in the southwest, excluding island territories. The coastline curves in a shallow S-shape following tectonic plate boundaries where the Eurasian, Philippine Sea, and Sunda plates meet, creating the continental shelf structure that defines Vietnam's maritime profile.
Ha Long Bay occupies 1,553 square kilometers of the Tonkin Gulf in Quảng Ninh Province, containing 1,969 limestone karst islands according to the 2000 Ministry of Culture survey that established current management boundaries. UNESCO inscribed the core zone as a World Heritage Site in 1994, expanding the designation in 2000 to include geological values spanning 500 million years of formation. The limestone towers rise from water depths averaging 10 meters, with some peaks reaching 200 meters above sea level. Hòn Gai port on the bay's eastern edge processes coal shipments from the nearby mines that have operated since French colonial extraction began in 1888. Tourist vessels departing from Tuần Châu Island marina numbered 523 boats in 2019 before the pandemic suspension, carrying an average of 4.2 million annual visitors during the 2015-2019 period.
The Red River enters Vietnam from Yunnan Province, China, flowing 510 kilometers through Vietnamese territory before dividing into nine distributaries that form the Red River Delta. The river's Vietnamese name Sông Hồng references the heavy silt load that colors the water reddish-brown during monsoon flows from May through October. The delta covers 15,000 square kilometers across eleven provinces and municipalities, supporting a population density of 1,200 persons per square kilometer according to 2019 General Statistics Office data. Hanoi sits 100 kilometers inland from the coast on the delta's apex where the river exits the northern highlands. The system deposits approximately 130 million tons of sediment annually, extending the coastline seaward at measured rates of 80 to 100 meters per century based on French survey benchmarks established in 1873 and Vietnamese resurveys completed in 1998 and 2015.
The Mekong River crosses into Vietnam from Cambodia near Tân Châu in An Giang Province, splitting immediately into two primary branches called Tiền Giang and Hậu Giang by Vietnamese geography. These channels subdivide into the network Vietnamese texts call Cửu Long Giang, the Nine Dragon River, though the number of active distributaries fluctuates seasonally between seven and thirteen depending on water levels. The Vietnamese portion of the Mekong Delta encompasses 39,000 square kilometers across thirteen provinces, terminating at four primary mouths on the South China Sea coast between Vũng Tàu and the Cà Mau Peninsula. Annual discharge volume averages 475 cubic kilometers, with peak flows during September and October reaching 40,000 cubic meters per second at Tân Châu gauging station. The delta supplies 50 percent of Vietnam's rice production from 1.9 million hectares of paddy cultivation, yielding 24.2 million tons in the 2020 harvest according to Ministry of Agriculture reporting.
Phú Quốc Island lies 45 kilometers west of Hà Tiên in the Gulf of Thailand, measuring 574 square kilometers with a north-south length of 50 kilometers. The island's highest point reaches 603 meters at Mount Chúa on the northern end. Phú Quốc became a district of Kiên Giang Province in 1956 after partition, upgrading to city status in 2021. Fish sauce production facilities line the western coast at Dương Đông town, where manufacturers ferment anchovies in wooden barrels following methods documented in Nguyễn dynasty trade records from 1823. Phú Quốc producers exported 14 million liters of fish sauce in 2019, maintaining the traditional 12-month fermentation period for premium grades. The international airport opened in 2012 with a 3,000-meter runway serving widebody aircraft. Pearl farms operate in the waters off the southern and eastern coasts, culturing Pinctada maxima oysters introduced from Australian stock in 1998.
The Central Coast runs 1,100 kilometers from the Hải Vân Pass north of Da Nang to Vũng Tàu, backed by the Annamite Range rising directly from narrow coastal plains that average 15 to 40 kilometers in width. The Hải Vân Pass crosses the range at 496 meters elevation, marking the meteorological boundary between northern and southern climate zones where the winter monsoon loses force. Highway 1A traverses the pass through a 6.3-kilometer tunnel completed in 2005, while the original French-era route built in 1826 remains open for local traffic. Da Nang occupies the coast immediately south of the pass, serving as Vietnam's fourth-largest city with a 2019 population of 1.13 million. The deep-water port at Tiên Sa handles container traffic and serves as the Vietnamese Navy's central logistics facility, established during American military operations in 1965 and expanded in 2018 with Chinese-built infrastructure financing.
Nha Trang Bay curves along 7 kilometers of coast in Khánh Hòa Province, sheltered by nineteen islands that create natural harbor conditions utilized since Cham maritime trade operated from the region between the 7th and 15th centuries. The Po Nagar Cham Towers stand on Cù Lao Hill north of the city center, with the main tower dated to 817 CE through inscriptions in Sanskrit and Cham script documented by French archaeologist Henri Parmentier in 1903. The Oceanographic Institute established operations in Nha Trang in 1923 under French administration, maintaining research stations and aquarium facilities that now operate under the Vietnam Academy of Science and Technology. Salt production pans extend along the coast south of the city, evaporating seawater in shallow beds to produce 47,000 tons annually according to 2018 provincial industry statistics.
Hội An occupies the north bank of the Thu Bồn River estuary, 4 kilometers from the South China Sea in Quảng Nam Province. The town functioned as a major Southeast Asian trading port from the 15th to 19th centuries, when Chinese, Japanese, Dutch, and Portuguese merchants established permanent quarters documented in European navigation charts from 1595 onward. The Japanese Covered Bridge spans a creek in the old town, constructed in 1593 according to foundation inscriptions and rebuilt in 1763 following storm damage recorded in French missionary accounts. UNESCO designated the ancient town center covering 30 hectares as a World Heritage Site in 1999, protecting 1,107 timber-frame buildings inventoried in the management plan. River siltation closed the port to ocean-going vessels by 1850, shifting major trade operations to Da Nang harbor 30 kilometers north. The Thu Bồn River rises 2 to 4 meters during October and November floods, requiring sandbagging of historic shophouses that maintain ground floors below the documented 100-year flood level of 3.8 meters established in provincial maps.
Vũng Tàu occupies a peninsula 125 kilometers southeast of Ho Chi Minh City where the Mekong Delta coastline meets the South China Sea. The city developed as a supply port during French colonial petroleum exploration beginning in 1865, when lighthouse construction commenced on the peninsula's southern tip at Mũi Nghinh Phong. Offshore oil production from the Bạch Hổ field started in 1986, located 130 kilometers southeast in waters averaging 60 meters depth. The field produced 12.4 million tons of crude oil in 2019 according to PetroVietnam annual reporting, supporting the refinery and port infrastructure that dominates Vũng Tàu's economy. Container shipping services connect to Singapore and Hong Kong through weekly vessel calls at Thị Vải port, which handles 1.8 million TEU annually based on 2019 throughput statistics.
The Côn Đảo Islands form an archipelago 185 kilometers offshore from Vũng Tàu, consisting of sixteen islands with a combined land area of 76 square kilometers. Côn Sơn, the largest island, measures 51 square kilometers and contains the district administrative center serving a permanent population of 7,200 residents recorded in the 2019 census. French colonial authorities established a prison on Côn Sơn in 1862, expanding the facility to contain 12,000 inmates in tiger cage cells that became internationally documented during the Vietnam War. The prison museum preserves 127 tiger cage structures, cement pits measuring 2.7 by 1.5 meters that held three to five prisoners each under conditions investigated by United States congressional staff in 1970. Côn Đảo National Park encompasses 80 percent of the archipelago's land area and 14,000 hectares of marine waters, protecting nesting sites for green sea turtles and hawksbill sea turtles. The airport on Côn Sơn operates a 1,830-meter runway serving turboprop aircraft on daily connections to Ho Chi Minh City, a route distance of 230 kilometers.
The Cà Mau Peninsula forms Vietnam's southernmost point at 8°36' North latitude, extending into the South China Sea where the Mekong Delta terminates in mangrove forests covering 41,862 hectares within Mũi Cà Mau National Park boundaries established in 2003. The cape at Đất Mũi reaches 275 kilometers south of Ho Chi Minh City, marked by a flagpole installed in 2000 at coordinates certified by the Ministry of Natural Resources and Environment. Mangrove restoration projects planted 15,000 hectares of Rhizophora apiculata and Avicennia alba between 1995 and 2015, replacing forest destroyed during wartime herbicide spraying and subsequent charcoal harvesting. Shrimp aquaculture ponds occupy 290,000 hectares across Cà Mau Province, producing 280,000 tons of black tiger prawns and whiteleg shrimp in 2019 according to provincial fisheries department statistics. The forest canopy reaches 12 to 18 meters height in mature sections, flooding twice daily with tidal ranges of 1.8 to 2.4 meters.
Cát Bà Island covers 285 square kilometers in the western sector of Ha Long Bay, administered as part of Hải Phòng municipality despite lying 30 kilometers from the city center. The island's interior contains Cát Bà National Park, established in 1986 to protect 109 square kilometers of limestone forest habitat. The park sustains a population of 60 to 70 golden-headed langurs, a critically endangered primate species endemic to this location and neighboring karst formations. The Cat Ba Langur Conservation Project documented 53 individuals in a 2019 census, down from an estimated 2,400 animals before hunting pressure intensified during the 1960s. The eastern coast contains three natural harbors where fishing boats operate from villages that collectively land 42,000 tons of marine catch annually, primarily squid and anchovy. Passenger ferries connect the main town of Cát Bà to Hải Phòng's Bến Bính terminal, a crossing of 18 nautical miles taking 45 minutes on hydrofoil vessels introduced in 2012.
Hải Phòng functions as northern Vietnam's primary seaport, located 120 kilometers east of Hanoi where the Cấm River meets the Bạch Đằng River before emptying into the Tonkin Gulf. The city administers 2,366 square kilometers including Cát Bà Island and portions of the Ha Long Bay coastline, with an urban population of 2.03 million recorded in 2019. The port complex handles 130 million tons of cargo annually across facilities at Nam Đình Vũ, Đình Vũ, and Lạch Huyện terminals. Container throughput reached 1.5 million TEU in 2019 according to Vietnam Seaports Association reporting. The Lạch Huyện International Port opened in 2018 on a dredged channel 13.5 meters deep, permitting 100,000-ton vessels to dock at berths previously limited to 30,000-ton capacity. Shipbuilding yards at Nam Triệu construct vessels up to 114,000 deadweight tons, launching eight ocean-going carriers in 2019. The port connects to Hanoi via the 105-kilometer Highway 5, upgraded to six-lane expressway standard in 2015 to reduce transit time to 75 minutes for container trucks.
Phan Thiết occupies the coast 200 kilometers northeast of Ho Chi Minh City where the Cà Ty River enters the South China Sea. The city's fishing fleet operates 1,800 vessels from ports at Mũi Né and Phan Thiết proper, landing 180,000 tons of fish in 2019 with anchovies comprising 62 percent of catch volume according to provincial statistics. Fish sauce production facilities process 45 percent of this catch in concrete fermentation tanks holding 50 to 200 cubic meters each. Mũi Né beach extends 15 kilometers east of the city center, backed by red and white sand dunes that reach 60 meters height. The white dunes near Bàu Trắng freshwater lake consist of quartz sand deposited by coastal erosion processes, with grain analysis showing 94 percent silica content. Wind patterns from the northeast monsoon deliver consistent speeds of 12 to 18 knots from November through March, supporting kitesurfing activity that drew 8,400 registered riders to competitions and training centers in 2019.
Quy Nhơn serves as the capital of Bình Định Province, occupying a bay 680 kilometers north of Ho Chi Minh City and 1,065 kilometers south of Hanoi. The city developed around a deepwater harbor protected by the Phương Mai Peninsula, which extends 3 kilometers into the South China Sea creating anchorage for vessels up to 50,000 tons. The port handled 9.8 million tons of cargo in 2019, primarily agricultural exports including rice, cashews, and black pepper from the Central Highlands interior. The Twin Towers of Quy Nhơn, locally called Thap Doi, date to the late 12th century during Cham occupation, standing 20 meters tall on Trầm Hương hill overlooking the harbor. Archaeological excavations in 1979 recovered Sanskrit inscriptions identifying the towers as dedicated to Shiva. Highway 19 connects Quy Nhơn to Pleiku in the Central Highlands across 175 kilometers of mountain road that climbs to 1,000 meters elevation at An Khê Pass.
The Gulf of Tonkin forms the northwestern corner of the South China Sea, bounded by the Vietnamese coast from Móng Cái to Thanh Hóa Province, China's Guangxi coast, and Hainan Island. The gulf covers approximately 126,000 square kilometers with an average depth of 50 meters. The Vietnamese and Chinese governments signed the Gulf of Tonkin Delimitation Agreement in 2000, establishing a maritime boundary that runs 644 nautical miles from the mouth of the Bắc Luân River to a point southwest of Hainan. The agreement allocated fishing zones and defined territorial waters, ending three decades of jurisdictional disputes that had escalated during the 1974 Paracel Islands confrontation. Vietnamese fishing boats operating in gulf waters numbered 31,000 vessels in 2018, harvesting primarily squid, mackerel, and tuna. The monsoon season from October through March generates waves reaching 3 to 5 meters height, suspending fishing operations for an average of 90 days annually.
Tam Cốc Bích Động lies 100 kilometers south of Hanoi in Ninh Bình Province, where the Ngô Đồng River cuts through limestone karst formations creating three caves spanning a total length of 600 meters. Rowboats transport visitors along the 2-kilometer river route, passing through the Hang Cả, Hang Hai, and Hang Ba caves at ceiling heights ranging from 2 to 20 meters. The karst landscape extends across 2,168 hectares within the Tràng An Landscape Complex, designated as a UNESCO World Heritage Site in 2014 for combined natural and cultural values. The limestone formations date to the middle Triassic period approximately 240 million years ago, composed of calcium carbonate deposited when the region lay beneath shallow tropical seas. Rice paddies occupy the valleys between karst towers, flooding from February through April and again from June through August during the two annual harvests that yield 8.5 tons per hectare according to provincial agricultural statistics.