Red Sea

• 1. Introduction

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  The Red Sea sits between Africa and Asia, a narrow corridor of water that carries roughly 12 percent of all global trade. Ships pass through it every day, threading between continents, and yet the sea they cross is one of the warmest and saltiest on Earth. It reaches a maximum depth of 2,730 meters in its central Suakin Trough, yet nearly a quarter of its total area is less than 50 meters deep. Those two facts, taken together, tell a larger story: this is a sea of extremes. Below its shallow shelves live more than 1,000 invertebrate species and 200 types of coral. Above them, vast volumes of cargo and energy move between continents. How did one body of water come to carry so much, harbor so much, and risk so much at the same time?

• 2. A Name With Many Meanings

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  Herodotus, writing in the fifth century BCE, used the names Red Sea and Southern Sea interchangeably, which offers the earliest clue that the color in this sea's name may have nothing to do with the water's appearance. One theory favored by some modern scholars connects the word red to the direction south, just as the name of the Black Sea may refer to north, drawing on a system in some Pre-Indo-European languages where colors stood for the cardinal directions. Another explanation points to seasonal blooms of the red-colored algae Trichodesmium erythraeum near the water's surface.

  The English name is a direct translation of the Ancient Greek Erythrà Thálassa. The Romans called it Mare Rubrum, Sinus Arabicus, and Pontus Herculis. In Arabic it is Al-Baḥr Al-Aḥmar. In Somali, Badda Cas. In Tigrinya, Qeyyiḥ bāḥrī. In Syriac, Yammāʾ summāqā. Each language preserved a version of the same root idea without any of them agreeing on exactly what that idea meant.

  The Hebrew term Yam Suph traces to the biblical account of the Israelites crossing the sea. Rabbi Saadia Gaon, writing between 882 and 942 CE, identified that crossing place specifically as Baḥar al-Qulzum, meaning the Gulf of Suez. Western geographers also recorded the sea under the names Mare Mecca and Sinus Arabicus, layering yet another identity onto a body of water that has never quite settled on a single one.

• 3. Ancient Ambitions

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  Around 2500 BCE, ancient Egyptians were already sailing the Red Sea in pursuit of trade with the land they called Punt. A second major expedition followed around 1500 BCE, this one organized by Hatshepsut. Both required long voyages south, and both reflected how early the sea was recognized as a passage to wealth.

  In the sixth century BCE, Darius the Great of the Achaemenid Empire sent reconnaissance missions into the Red Sea specifically to chart its navigational hazards: the rocks, the currents, the places where ships could be lost. The practical outcome was a canal linking the Nile River to the northern end of the Red Sea at Suez. Darius commemorated its completion with stelae, stone monuments inscribed in multiple languages, describing the canal and its benefits. That waterway is sometimes called the ancient Suez Canal, and its construction was recorded in ancient inscriptions that survive today.

  In the late fourth century BCE, Alexander the Great dispatched Greek naval expeditions down the Red Sea toward the Indian Ocean. The scholar Agatharchides collected data on the sea in the second century BCE. Around the first century CE, an unknown Greek author produced the Periplus of the Erythraean Sea, a detailed navigation guide listing the Red Sea's ports and sea routes, and noting how a navigator named Hippalus first identified the direct route from the Red Sea outward. By the reign of Augustus, the Roman Empire had made the Red Sea its favored corridor for trade with India, and through Indian ports, goods originating in China reached Rome. That connection was severed around the third century CE when the Aksumite Empire disrupted the route.

• 4. Medieval Power and Passage

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  In 1183, a Crusader lord named Raynald of Châtillon launched a fleet down the Red Sea with the aim of attacking Muslim pilgrim convoys bound for Mecca. The raid sent a wave of anger through the Muslim world, driven partly by the belief that Raynald intended to strike the holy cities themselves. The source notes that Raynald's actual target appears to have been the lightly armed pilgrim convoys rather than the well-guarded cities, but the perception of the threat shaped the political consequences regardless.

  By 1513, the Red Sea had become a contested prize between competing empires. Afonso de Albuquerque led the first European fleet in modern times to sail through the Bab al-Mandab in an attempt to secure the sea route for Portugal, laying siege to Aden before being forced to retreat. A decade later, in 1524, Aden was handed to a Portuguese governor under an arrangement for protection against the Ottoman Empire.

  In 1798, France ordered Napoleon I to invade Egypt partly to gain control of the Red Sea. He failed, but his expedition produced a lasting consequence: the engineer Jean-Baptiste Lepère joined the campaign and revived the long-dormant concept of a canal between the Mediterranean and the Red Sea. The Suez Canal that finally opened in November 1869 traced a line first imagined during the reign of the pharaohs, interrupted by Darius, and repeatedly reconsidered across centuries. After the Second World War, oil tanker traffic through the canal intensified sharply. The Six-Day War then closed it entirely from 1967 to 1975, a disruption long enough that the Cape of Good Hope route around Africa recovered a competitiveness it has never entirely lost.

• 5. A Living Seafloor

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  The Red Sea sits atop the Red Sea Rift, a section of the Great Rift Valley where the Arabian Peninsula is slowly pulling away from the Horn of Africa. That separation began in the Eocene and accelerated through the Oligocene. In 2005, following three weeks of tectonic activity, the sea had measurably widened by 8 meters. Scientists consider it likely to become an ocean in time, following the model proposed by John Tuzo Wilson.

  In 1949, a deep water survey found unexpectedly hot brines in the central portion of the sea. Follow-up work in the 1960s confirmed water temperatures of 60 degrees Celsius in those brines, along with metalliferous muds emanating from an active subseafloor rift. Lake Asal in Djibouti has been identified as a useful site for studying how those deep brine pools evolve, because its salt composition represents something close to the compositional extreme of the Red Sea's own deep waters.

  Volcanism still shapes the sea's surface. In 2007, Jabal al-Tair island in the Bab el Mandeb strait erupted violently. Two new islands then emerged in the Zubair Archipelago, a chain owned by Yemen: Sholan Island appeared in December 2011, and Jadid followed in September 2013. The sea's geological youth means its mineral inventory is still forming. Estimates of undiscovered oil reserves in the region reach more than 5,000 million barrels. Gas reserves are estimated at more than 112,000 billion cubic feet. The Durwara 2 oil field was discovered in 1963; the Barqan Field in 1969; the Midyan Field in 1992. The salt deposits of the Middle Miocene, buried below the seafloor, help govern where those fossil energy resources can be found.

• 6. A Sea Alive

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  More than 1,200 fish species have been recorded in the Red Sea, and 10 percent of them are endemic, meaning they exist nowhere else on Earth. The lyretail anthias is described as the most commonly found fish in the sea. Among the 44 recorded shark species are whale sharks, tiger sharks, and great hammerheads. In December 2024, a false killer whale was discovered off the coast of Saudi Arabia. A blue whale was sighted in the Gulf of Aqaba in 2018.

  The coral reefs extending roughly 2,000 kilometers along the coastline are between 5,000 and 7,000 years old. They are formed mainly from stony acropora and porite corals and include formations that do not fit standard Darwinian reef classification schemes, likely because of the area's high tectonic activity. The Blue Hole at Dahab, a cylinder-shaped formation, is among the distinctive results. Egypt established the Ras Mohammed National Park in 1983 to protect the local marine ecosystem; it is recognized by the International Union for Conservation of Nature as one of the world's top ten sites for effective marine management, and it was the first marine protected area anywhere in Africa and the Middle East.

  Since the Suez Canal opened in November 1869, more than a thousand marine species from the Red Sea have migrated northward into the Mediterranean. Plankton, seaweeds, invertebrates, and fish have all made the crossing, and a number of those species now form a significant component of the Mediterranean ecosystem. Scientists working with the Mediterranean Science Commission have found that this shift is currently accelerating, particularly among fish. A virus called BA3, found in Favia favus coral near Sudan and Eritrea, kills the white plague agent Thalassomonas loyana, suggesting the sea contains its own biological defenses that researchers are now studying for possible application elsewhere.

• 7. Trade, Tourism, and Risk

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  Twelve percent of global trade passes through the Red Sea, including 30 percent of global container traffic. Ships traveling between the Indian Ocean and the Mediterranean save roughly half the distance they would cover by sailing around Africa. At least 18 desalination plants line the Saudi coastline alone, meeting the water needs of the region's population and industries while discharging warm brine and treatment chemicals that bleach coral and cause disease in fish.

  The sea became a recreational destination after Hans Hass conducted diving expeditions in the 1950s, followed by Jacques-Yves Cousteau. Sites including the SS Thistlegorm shipwreck, Elphinstone Reef, and the Sudanese reefs at Sanganeb and Shaab Rumi attract divers from around the world. In December 2010, the beach at Sharm el-Sheikh was closed to swimming following several serious shark attacks, including one fatality. Scientists investigating the attacks identified possible contributing factors including overfishing, tourist boat operators chumming offshore for shark photography, and ships discarding livestock overboard. The sea's geography plays a role too: its narrow width, significant depth, and sharp drop-offs allow large deep-water sharks to roam in hundreds of meters of water while remaining within a hundred meters of swimming areas.

  Since November 2023, Houthi forces have conducted more than 100 attacks on commercial and naval vessels near the Bab al-Mandab. In January 2024, Red Sea shipping volumes fell to 30 percent of normal levels. Container vessel traffic through the Suez Canal declined by approximately 75 percent in 2024 compared to 2023. Ships rerouting around the Cape of Good Hope travel 50-60 percent longer distances, adding roughly 4,575 nautical miles between Shanghai and Rotterdam and extending voyages by an average of 12 days. Fuel consumption rises by up to 33 percent on those longer routes, and CO2 emissions per voyage increase by approximately 40 percent. For a typical weekly Asia-North Europe service, total fleet CO2 emissions rose by an estimated 67 percent. The sinking of the MV Rubymar in February 2024 released approximately 200 tons of heavy fuel oil and 80 tons of marine diesel oil, creating an 18-mile oil slick that drifted toward the Farasan Islands and the Dahlak Archipelago. The vessel also carried 21,000 metric tons of fertilizer, raising the risk of algal blooms in the surrounding water. In January 2025, the United Nations Security Council adopted Resolution 2768 calling for an end to Houthi attacks and demanding the release of crews from seized vessels.