Top 10 Largest Bays in the World

#1: Bay of Bengal (Area: 748,000 sq mi)

Spanning roughly 748,000 square miles between India, Bangladesh, Myanmar, and the Malay Peninsula, the Bay of Bengal is Earth’s largest bay. Its broad surface collects the outflow from the Ganges, Brahmaputra, and Irrawaddy rivers, depositing a record-breaking sediment load that built the Sundarbans—an immense mangrove forest home to Bengal tigers and estuarine crocodiles. Early traders harnessed the monsoon winds to sail dhows laden with spices and silks, linking distant ports as early as the 3rd century BCE. Beneath its muddy waters lie deep submarine canyons carved by ancient rivers, now over 10,000 feet below sea level. The bay’s seasonal cyclones shape coastal life: in 1970, a devastating storm surge claimed over half a million lives in then-East Pakistan. Modern efforts by the Bay of Bengal Initiative (BIMSTEC) foster cooperation on fisheries, shipping, and disaster preparedness. Hidden marvels include coral atolls in the Andaman and Nicobar archipelago, where underwater caves shelter rare fish species. The Bay of Bengal remains a dynamic frontier where natural forces and human history converge on an almost unimaginable scale.

#2: Gulf of Mexico (Area: 600,000 sq mi)

Enclosed by the United States, Mexico, and Cuba, the Gulf of Mexico covers about 600,000 square miles. Its warm Loop Current, a branch of the Atlantic’s Gulf Stream, moderates coastal climates from Florida’s beaches to Veracruz’s oil rigs. Spanish explorers of the 16th century dubbed it “Mar de las Calmas” for its deceptively calm surface. Below, the Sigsbee Deep—a basin plunging over 14,300 feet—hosts methane seeps that feed specialized mussels and worms adapted to darkness and extreme pressure. The gulf’s barrier islands buffer inland areas from hurricanes, yet disasters like Hurricane Katrina in 2005 exposed vulnerabilities in levee systems. The 2010 Deepwater Horizon spill highlighted environmental risks of offshore drilling, spurring large-scale restoration and stricter regulations. Biologically, the gulf teems with bluefin tuna spawning grounds, nesting sea turtles, and migratory birds in coastal marshes. Hidden seagrass meadows off the Florida Panhandle shelter manatees, while artificial reefs around oil platforms have become nurseries for fish. From ancient shipwrecks preserving artifacts to thriving marine life, the Gulf of Mexico’s vast waters continue to shape regional culture and commerce.

#3: Gulf of Guinea (Area: 386,000 sq mi)

Along West Africa’s shores from Senegal to Angola, the Gulf of Guinea spans roughly 386,000 square miles. Named for the medieval Ghana Empire, it fed trans-Saharan trade routes and later colonial ambitions for gold and spices. Today, its equatorial currents drive upwelling zones that support prolific fisheries for sardines and anchovies, essential to coastal communities. Offshore, Nigeria and Angola’s oil fields rank among the globe’s most productive, yet oil pollution and gas flaring threaten mangrove ecosystems in the Niger Delta, one of the world’s largest wetlands. Submarine canyons here nurture shrimp and deep-sea fish around methane seeps, revealing chemosynthetic life miles beneath the surface. Onshore, mangroves protect villages from storm surges and provide nurseries for juvenile fish. Cultural legends speak of Mami Wata, water spirits thought to inhabit lagoons and estuaries—a confirmation to the gulf’s enduring place in local folklore. Marine conservation initiatives now focus on preserving mangrove belts and regulating offshore drilling to safeguard both biodiversity and livelihoods in this expansive, historic bay.

#4: Gulf of Alaska (Area: 587,000 sq mi)

Bordering Alaska’s southern coast and the Aleutians, the Gulf of Alaska covers about 587,000 square miles. Fed by glacial melt and North Pacific storms, its cold, nutrient-rich waters drive colossal salmon runs that attract grizzlies to coastal streams. Russian fur traders named Kodiak Island “Alashka” (great land), sensing its wild potential. Beneath its surface lies Kodiak Canyon, plunging over 18,000 feet, where hydrothermal vents nurture shrimp and tubeworms in near-freezing water. The 1989 Exxon Valdez spill in Prince William Sound led to sweeping environmental reforms and long-term shoreline monitoring. Tidewater glaciers like Columbia and Hubbard regularly calve icebergs into deep fjords, creating brine-driven currents that transport oxygen-rich water to abyssal depths. Hidden geothermal springs on the Kenai Peninsula bubble forth along remote beaches, offering natural hot pools amid snow-clad forests. The Trans-Alaska Pipeline dumps crude into Valdez, underscoring the gulf’s economic importance. From ancient petroglyphs on the Katmai coast to modern whale-watching excursions, the Gulf of Alaska remains a realm of stunning landscapes and ecological resilience.

#5: Hudson Bay (Area: 316,000 sq mi)

Encompassing roughly 316,000 square miles in northeastern Canada, Hudson Bay is vast yet surprisingly shallow, with an average depth under 300 feet. Carved by Pleistocene glaciers, its inner basin is ringed by tundra and boreal forest. In 1610, Henry Hudson navigated its frozen entrance, naming the bay for himself and paving the way for the Hudson’s Bay Company’s fur trade—one of North America’s first multinational enterprises. Each winter, up to four feet of sea ice forms, enabling dog-sled travel and polar bear hunts on the pack. Beluga whales annually return to its estuaries, where researchers track migrations via acoustic tagging. On its southern shores, Churchill, Manitoba, hosts tens of thousands of tourists drawn to polar bear viewing, giving rise to the “Polar Bear Capital” moniker. Geological surveys have identified kimberlite pipes near Baker Lake, fueling diamond exploration. Medieval trading posts like York Factory now lie preserved as archaeological parks accessible only by boat or floatplane. Hidden sulfide springs in Wapusk National Park create isolated warm-water pools where stunted willows sprout amid permafrost. Hudson Bay’s shallow seas, storied history, and extreme seasons make it a bay like no other.

#6: Bay of Biscay (Area: 190,000 sq mi)

Off the western coasts of France and Spain, the Bay of Biscay spans about 190,000 square miles. Its deep Continental Shelf drop-offs—over 10,000 feet—funnel nutrient-rich waters to continental slopes, fueling robust fisheries for hake and tuna. The bay’s stormy winters, fed by Atlantic depressions, challenged ancient mariners; Celtic legends speak of the “sea of storms” that tested the courage of seafarers. Canadian warships once used Biscay lanes to evade U-boats in WWII, and ruins of coastal forts still stand sentinel. Offshore, the Bay of Biscay hosts breathable ridges of cold-water corals, abandoned oil rigs converted to artificial reefs, and vent-fed mud volcanoes supporting chemosynthetic fauna. Hidden sandy coves like Ploumanac’h in Brittany reveal pink granite outcrops sculpted by millennia of waves. The Bilbao estuary’s revival—once a toxic shipping channel transformed into a cultural hub with Guggenheim Bilbao—demonstrates the bay’s potential for renewal. From pilgrimage ports like Saint-Jean-de-Luz to migrant-bird flyways, the Bay of Biscay weaves natural drama with human resilience.

#7: Gulf of Carpentaria (Area: 186,000 sq mi)

Enclosed by northern Australia, the Gulf of Carpentaria covers roughly 186,000 square miles and plunges less than 250 feet deep. Aboriginal clans of Arnhem Land and Cape York Peninsula have fished its turbid waters for millennia, using bark canoes to harvest prawns and dugong. Seasonal monsoons flood inland channels, transforming savannas into wetlands teeming with waterbirds and crocodiles. Dutch navigator Jan Carstensz first mapped the gulf in 1623, naming Cape Keerweer for his forced retreat by hostile shores. Geological surveys reveal phosphate-rich sediments from the Miocene era, now under discussion for seabed mining. Hidden mudflats around Groote Eylandt host the world’s oldest shipwreck—a 17th-century VOC merchantman, the Zelandia, unearthed by shifting tides. Mangrove forests along the gulf’s margins store carbon at rates rivaling tropical rainforests, offering natural climate mitigation. From indigenous rock art depicting marine life to modern fish trawlers, the Gulf of Carpentaria remains a crossroads of culture, ecology, and paleoclimate archives.

#8: Bay of Campeche (Area: 87,000 sq mi)

The Bay of Campeche, forming the southern arc of the Gulf of Mexico, spans about 87,000 square miles off Mexico’s Yucatán Peninsula. Named after the port of Campeche—once a Spanish treasure hub—the bay held strategic importance for colonial galleons transporting New World silver. Beneath its waters lies the Campeche Bank, a shallow carbonate platform studded with coral reefs that shelter snappers and grouper. Offshore basins trap vast Pliocene-Pleistocene hydrocarbon deposits; PEMEX platforms stand sentinel over pump jacks and pipelines. In 2020, geologists imaged overpressured mud volcanoes that belch methane and sustain chemosynthetic worm colonies. The bay’s estuaries—such as Laguna de Términos—harbor endangered West Indian manatees and olive ridley turtles nesting on remote beaches. Fisherfolk in Campeche’s coastal villages still set out at dawn in wooden pangas to harvest spiny lobster using century-old traps. Submerged Mayan canoe wrecks, discovered near Holbox Island, speak of pre-Columbian trade in salt and honey. The Bay of Campeche’s confluence of geological wealth and living ecosystems underscores its vital role in Mexico’s cultural and economic tapestry.

#9: Bay of Bothnia (Area: 77,000 sq mi)

Between Sweden and Finland, the Bay of Bothnia covers about 77,000 square miles but reaches an average depth under 200 feet. This northern bay freezes every winter, creating ice roads that connect island communities. The land is rising—rebounding after the last ice age at up to a tenth of an inch per year—slowly creating new skerries and peat-bog marshes. Hanseatic merchants once sailed its brackish waters to trade in herring and fur, founding ports like Vaasa and Umeå. Biologists study its unique brackish fish populations, such as the Bothnian herring adapted to low salinity. The Kvarken Archipelago—now a UNESCO World Heritage site—hosts island-hopping trails through post-glacial uplift landscapes. Hidden hot springs near Kuusamo feed thermal pools in the snow, a warming oasis for winter travelers. The Bay of Bothnia’s blend of glacial rebound, cultural history, and ecological peculiarities offers a distinctive bay framed by boreal forests and granite islets.

#10: Gulf of Thailand (Area: 59,000 sq mi)

Indenting the shores of Thailand, Cambodia, and Vietnam, the Gulf of Thailand spans roughly 59,000 square miles. Its shallow continental shelf—mostly less than 200 feet deep—warms quickly under the tropical sun, fueling monsoon-driven fisheries of anchovy, mackerel, and squid. Early Chinese junks and Khmer vessels navigated its mild waves, trading silk and porcelain at port cities like Ayutthaya and Sihanoukville. The bay’s mudflats around Pattani Bay support vast flamingo populations, while seagrass meadows near Ko Samui shelter dugongs. Hidden limestone karst islands, such as Koh Samet and Koh Chang, rise dramatically from turquoise waters, their caves hiding prehistoric cave art. Offshore oil platforms near the Gulf of Thailand’s basins pump light crude, balancing energy extraction with marine conservation zones. Coral reefs at Koh Tao host vibrant dive communities, and researchers tag whale sharks that gather annually to feed on plankton blooms. The Gulf of Thailand’s cultural heritage, seasonal rhythms, and coastal beauty make it a vibrant tropical bay at the heart of Southeast Asia.

From the sediment-laden Bay of Bengal to the ice-bound Bay of Bothnia, the world’s largest bays reveal the power of water to sculpt continents, sustain wildlife, and shape human history. Each bay—whether driven by monsoon winds, tide-forced estuaries, or glacial rebound—offers unique ecological riches, hidden geological formations, and stories of exploration that span millennia. As climate change and human activity reshape these coastal giants, understanding their past and present becomes crucial to stewarding their future.