Archeologists Just Found an Underwater Graveyard Packed with Punic, Roman, Medieval, and World War II Shipwrecks

The bottom of the Bay of Algeciras is a museum no one built on purpose. For thousands of years, ships that anchored there waiting for safe passage through the Strait of Gibraltar never left. They went down in storms, in battle, or because the sea simply decided otherwise. Now archaeologists have catalogued what remains.

A three-year survey called Project Herakles logged 151 archaeological sites across a 29-square-mile stretch of water between the Spanish city of Algeciras and the British territory of Gibraltar. More than 100 of those sites are shipwrecks. The oldest dates to the fifth century B.C., when Carthage controlled the western Mediterranean. The most recent is a weapon from World War II.

The finds compress Punic trade, Roman expansion, medieval seafaring, and 20th-century naval warfare onto a single patch of seabed. “There are really few places in the Mediterranean that have this kind of concentration and such a significant variety of archaeological remains,” Felipe Cerezo Andreo, an underwater archaeologist at the University of Cádiz who led the study, told the Guardian.

The Trap at the Mouth of the Mediterranean

The Strait of Gibraltar is the only seam between the Mediterranean Sea and the Atlantic Ocean. Every vessel making that transit contended with hard currents, sudden weather shifts, and the politics of a chokepoint. The Bay of Algeciras, tucked against the strait’s eastern entrance, served as the holding pen. Captains anchored there to wait out bad conditions, sometimes for days.

“All vessels that want to go from the Mediterranean to the Atlantic have to pass through the Strait of Gibraltar, and probably most of them have to anchor and wait for better weather conditions in the Bay of Algeciras,” Cerezo Andreo told CNN.

That waiting turned lethal with enough frequency to seed the seafloor with wrecks. The bay recorded two major naval battles: the Battle of Gibraltar in 1607 and the First Battle of Algeciras in 1801. In that second engagement, British Rear Admiral James Saumarez, his squadron badly damaged on July 6, retreated to Gibraltar, repaired his ships, and sailed back out six days later to defeat a larger combined French and Spanish force, as documented by the Society for Nautical Research. Outside of wartime, ordinary transit failures stacked hulls atop hulls for centuries.

Carthaginians, Romans, and Ships Nobody Expected

The Roman period accounts for 25 of the documented wrecks, a number that tracks with the empire’s centuries-long grip on both shores of the strait. The oldest vessel belongs to the Punic era, a remnant of Carthaginian maritime power around the fifth century B.C., well before Rome erased Carthage from the map. A University of Cádiz research portal entry notes that geophysical surveys and visual inspections confirmed two Punic shipwrecks, recovered materials from two anchorage zones, and flagged two more potential wrecks awaiting confirmation.

Three medieval wrecks caught the team off guard. Ship timbers from that period are scarce across the Mediterranean. Cerezo Andreo told the Guardian that studying those hulls could illuminate seafaring during the late centuries of Islamic rule in southern Spain, an era with a thin material record.

By the early modern period, the bay had become international in a way few harbors were. The team documented Dutch, Venetian, Spanish, and English ships. “We have ships of practically every nationality, because they all passed through the strait,” Cerezo Andreo told the Guardian. Popular Mechanics reported that 134 shipwrecks were catalogued overall, with 34 documented in full.

A Gunboat That Hid Beneath Fishing Nets

The wreck of Puente Mayorga IV stands out because of the strategy it was built to execute. Spain designed this small gunboat in the 18th century to harass British shipping near the Rock of Gibraltar, the territory Britain secured in 1713 through the Treaty of Utrecht.

The vessels dressed as fishing boats, netting concealing cannons until the crew dropped the disguise and opened fire at close range. Historians knew the tactic from written records. A physical example had never been studied until now.

The team also identified a Maiale, Italian for “pig,” a World War II human torpedo. Italian Navy divers straddled these slow-moving weapons, steered toward anchored enemy ships, clamped explosive charges to the hull, and withdrew before detonation. Italy relied on the devices when its surface fleet could not match Allied numbers in the Mediterranean.

A Seabed Blanketed by an Invader

Documenting the wrecks means racing against industry and biology. The Bay of Algeciras remains one of Europe’s most heavily used maritime zones. Shipyards, oil refineries, and dredging operations grind at the seabed. Sediment patterns have shifted under pressure from climate change and port construction, exposing some material and burying the rest deeper with little predictability.

Then there is the algae. Rugulopteryx okamurae, a brown seaweed native to the Northwest Pacific, turned up in the region several years ago and spread fast. It forms dense mats that smother native species and block visual surveys. In five years, it has swallowed wrecks that sat exposed for centuries.

According to El País, the research team used underwater photographs from the 1970s and 1980s to relocate several known sites and measure how much the marine environment has changed under the weight of this invasive species.

Anchors, Archives, and What Comes Next

The survey covered just 23 percent of the bay’s surface, mostly nearshore zones. Deeper water introduces a different threat. Large cargo vessels drop anchors weighing more than twenty tons, and when they hit, the damage is immediate.

The team’s assessment classifies 56 percent of the documented sites as stable. The other 44 percent require urgent study and protection. Researchers are pushing for formal underwater cultural heritage designations that would restrict anchoring and development in the most sensitive areas.

While that legal effort proceeds, the data gets a second life. The team is building a public digital archive of 360-degree dive videos and three-dimensional virtual models, allowing researchers and the public to examine the wrecks without disturbing them. The long task of interpreting those hulls, and deciding what can be saved, has only started.

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