Here’s what you’ll learn when you read this story:

• Researchers discovered a heavily armed 18th-century Barbary corsair ship between Morocco and Spain, the first of its kind found in the region's waters.

• The pirate vessel, armed with cannons, swivel guns, and muskets, was discovered in 2005 while explorers were searching for a different shipwreck.

• Dating from around 1740-1760, the corsair ship provides valuable insights into the Barbary pirates who terrorized Mediterranean nations for over a century

Decades ago, divers discovered a heavily armed, 18th-century pirate ship in the waters between Morocco and Spain. Armed to the teeth, it now sits at the bottom of the ocean, serving as an example of an enterprise that terrorized the seas off the coast of Africa for over a century. The ship, known as a Barbary corsair, was “the first Algiers corsair found in the Barbary heartland,” Sean Kingsley, an archaeologist and researcher on the discovery, told Live Science.

Barbary corsairs—the name for both the ships and those who crewed them—were privateers who sailed for several countries along the northern coast of Africa. Often referred to as pirates, they ruled the Mediterranean from the 17th century until the early 19th century, when they fell after the Second Barbary War. “Less famous than the pirates of the Caribbean, the corsair capital of Algiers turned to piracy far earlier and was a much bigger business,” Kingsley told Newsweek. “Where Blackbeard and his gang put the fear of God into single ships, the Barbary pirates terrorized entire nations.”

Yet it seems even they were no match for an unexpected storm, which is considered the most likely reason for the ship ending up at the bottom of the sea. The shipwreck was originally discovered in 2005 by the Odyssey Marine Exploration (OME). At the time, the Florida-based company was searching for the HMS Sussex—an 80-gun English warship that was lost in 1694—but stumbled across the corsair along the way.

To investigate their surprise pirate treasure, the research team navigated a remotely operated vehicle to the ship and discovered that it was armed with four large cannons, 10 swivel guns, and plenty of muskets for its 20-pirate crew. Pots and pans from the city of Algiers—once a hub for the Barbary corsairs—were also found in the wreckage, leading the experts to believe that the ship may have disguised itself as a trading vessel. They suggested that the ship could have been on its way to the Spanish coast to capture and raid settlements when it sank.

Researchers used artifacts from the vessel to determine when the ship may have sailed. “The tightest dating comes from the glass bottles that were blown, at latest, 1740-1760. So the ship can’t postdate 1760,” Kingsley told Newsweek.

Other findings on board—such as a European “spyglass,” ceramics, and bowls—also suggest a similar timeframe. According to Newsweek, however, it’s not yet possible to determine the date the ship was constructed or how long it was in service.

Parts of the wreckage, according to Archaeology Magazine, were well preserved. The lower third of the hull in particular had remained undisturbed by divers or fishing boats for the past four centuries. Unfortunately, the upper parts of the Barbary ship were destroyed by shipworms—the termites of the sea.

That doesn’t mean, however, that the researchers are unhappy with the information they’ve gleaned from the wreck. The Barbary corsair provides a glimpse into what the 17th century seas may have looked like.

“The threat of Algiers’ corsairs was an everyday terror for the West,” Greg Stemm, Director of Seascape Artifact Exhibits Inc., told Newsweek. “The shipwreck found in deep waters is a precious echo of one of the western Mediterranean’s great maritime horrors.”