A handful of narrow waterways carry an outsized share of global trade, and their geography makes them both strategically vital and politically sensitive. The Strait of Gibraltar separates Spain in Europe from Morocco in Africa and links the Atlantic Ocean to the Mediterranean Sea; at its narrowest it measures only about 14 kilometers across. The Strait of Hormuz, around 21 kilometers wide at its narrowest, lies between the Persian Gulf and the Gulf of Oman, and roughly 20% of the world's petroleum passes through it every year. Farther east, the Strait of Malacca runs between the Malay Peninsula and the Indonesian island of Sumatra, forming one of the world's busiest shipping lanes connecting the Indian and Pacific Oceans.
The Bosphorus Strait runs through Istanbul, Turkey, separating Europe from Asia and providing the only water link between the Black Sea and the Mediterranean system. The Strait of Magellan offers a navigable passage between mainland South America and Tierra del Fuego, allowing ships to traverse between the Atlantic and Pacific without rounding Cape Horn. The Drake Passage, between Cape Horn and the South Shetland Islands off Antarctica, connects the Atlantic and Pacific at the southern tip of the Americas and is famous as one of the roughest waterways in the world. The Torres Strait lies between Australia and Papua New Guinea, joining the Coral Sea to the Arafura Sea.
Canals have reshaped maritime geography by allowing ships to bypass long and dangerous detours. The Suez Canal, opened in 1869 and located entirely in Egypt, runs about 193 kilometers between the Mediterranean Sea and the Red Sea, eliminating the need to sail around Africa. The Panama Canal, completed in 1914, links the Atlantic and Pacific across the Isthmus of Panama using a system of locks — Gatun, Pedro Miguel, and Miraflores — that raise and lower vessels about 26 meters as they cross the continental divide through Gatun Lake. A 2016 expansion, known as the Third Set of Locks, now permits passage of much larger Neopanamax ships carrying nearly three times the cargo of the original locks.
Other canals and shipping lanes round out the network of global waterways. The Kiel Canal in northern Germany, about 98 kilometers long, links the North Sea to the Baltic Sea and is among the world's busiest artificial waterways. The Grand Canal of China stretches roughly 1,776 kilometers from Beijing to Hangzhou and is the longest artificial waterway on Earth, originally constructed more than two millennia ago. The Northern Sea Route runs along Russia's Arctic coast and is becoming increasingly navigable as melting sea ice extends the shipping season, while the historic Cape of Good Hope route around southern Africa remains a critical alternative for vessels too large for the Suez Canal. The English Channel separates England from France across roughly 560 kilometers and narrows to about 34 kilometers at the Strait of Dover. Long before modern shipping, the Silk Road of the Sea connected China to Southeast Asia, India, Arabia, and East Africa, carrying silk, spices, and porcelain across the Indian Ocean.