Archaeologists have made a remarkable discovery off the coast of Costa Rica, identifying two 18th-century shipwrecks as Danish slave ships rather than pirate vessels as previously believed.
The ships, which have rested in shallow waters off Cahuita National Park for more than three centuries, were excavated in 2023.
However, it was only recently that researchers confirmed their true identity through detailed analysis of artefacts and materials recovered from the site.
The vessels, named Fridericus Quartus and Christianus Quintus, were shipwrecked in 1710 in what has been described as one of the most dramatic shipwrecks in Danish history.
The shipwreck was originally discovered in 2023
NATIONAL MUSEUM OF DENMARK
According to the National Museum of Denmark, the Fridericus Quartus and Christianus Quintus met different fates during the 1710 incident.
“Fridericus Quartus was set ablaze, while Christianus Quintus had its anchor rope cut, following which the ship was wrecked in the surf,” the museum stated.
Until the recent discovery, the exact location of these ships had remained a mystery.
Images from the excavation show divers examining the shipwrecks, which display significant deterioration after 315 years underwater.
The vessels had long been misidentified as pirate ships by locals and earlier researchers.
The excavation process involved collecting various samples from the shipwrecks, including wood from the vessels and yellow bricks that formed part of their cargo.
Researchers also recovered clay pipes during the underwater exploration.
These artefacts proved crucial in establishing the ships’ true identity.
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The vessels had long been misidentified as pirate ships by locals and earlier researchers
NATIONAL MUSEUM OF DENMARK
The yellow bricks were particularly significant as they were produced in Flensburg “for use in Denmark and in the Danish colonies in the 18th and 19th centuries,” according to the museum.
“The clay comes from Denmark — quite specifically, from either Iller Strand or Egernsund,” both located by Flensburg Fjord, an area known for its brick-producing industry in the 18th century.
The recovered items showed clear signs of the ships’ dramatic end, with wood samples bearing evidence of fire damage.
Scientists employed dendrochronological analysis—tree-ring dating—to determine the origin of the wood used in the ships’ construction.
The analysis revealed that “the timbers originate in the western part of the Baltic Sea,” encompassing northeastern Germany, Schleswig-Holstein, Denmark and Scania.
Researchers determined the trees were felled between 1690 and 1695.
The charred and sooty condition of the wood corroborated historical accounts of one ship being set ablaze.
The clay pipes found at the site were identified as “ordinary, Dutch-produced pipes that were also used onboard Danish ships.”
The yellow bricks were particularly significant as they were produced in Flensburg ‘for use in Denmark and in the Danish colonies in the 18th and 19th centuries,’ according to the museum
NATIONAL MUSEUM OF DENMARK
Their size, shape and patterns indicated they were manufactured shortly before the 1710 shipwreck.
After thorough examination at the National Museum of Denmark and the University of Southern Denmark, researchers confirmed the vessels’ identities.
David Gregory, a marine archaeologist at the National Museum of Denmark, expressed confidence in their findings.
He said: “The analyses are very convincing and we no longer have any doubts that these are the wrecks of the two Danish slave ships.
“The bricks are Danish and the same goes for the timbers, which are additionally charred and sooty from a fire. This fits perfectly with the historical accounts.”
His colleague Andreas Kallmeyer Bloch described it as “undoubtedly the craziest archaeological excavation I’ve yet been part of.”
Bloch added: “Not only because it matters greatly to the local population, but also because it’s one of the most dramatic shipwrecks in the history of Denmark.
“This provides two pieces that have been missing from the history of Denmark.”
