Pipeline Workers Found a 400-Year-Old Shipwreck in the Baltic, and One Object on Board Still Baffles Experts

Off Germany’s Bay of Greifswald, the kind of underwater survey that usually produces charts and clearance reports instead turned up a badly deteriorated wooden sailing vessel buried in heavy silt about 25 feet down, right in the path of a planned gas pipeline near Lubmin. A five-person crew of commercial divers and maritime archaeologists squeezed in 22 dives over a little more than 12 days before dredging resumed, documenting more than 60 artifacts from shoe soles to pulley blocks. Tree-ring dating on recovered oak timbers places the ship in the early 1600s, but one find is still resisting every tidy label: a flat yellowish clay brick pierced with four or five cone-shaped holes and fitted tightly into an oak block. “To date, no direct parallels or definitive explanation of the object’s function have been identified,” University of Warsaw underwater archaeologist Michał Grabowski wrote.

A pipeline survey rarely reads like a page-turner. Yet in northern Germany, a pre-construction check for an underwater gas line turned into the kind of discovery that makes engineers and archaeologists share the same anxious calendar. The story, first aired broadly in September 2026 coverage, starts with a muddy patch of Baltic water and ends with a small object nobody can quite explain.

The unexpected find beneath the Baltic

During 2023 survey work in the Bay of Greifswald, crews found a previously unknown, highly deteriorated wooden sailing vessel where a pipeline route was being prepared. The wreck sat in heavy silt under about 25 feet of water, near the mouth of the Peene Strait and roughly 1.9 miles north of the LNG facility at Lubmin. The initial report describes it as a clinker-built hull, with planks fastened by iron nails and sealed with a mix of tar and animal hair, per discovered in 2023 coverage.

Tree rings, fast dives, and a working ship

The ship’s age was pinned down through dendrochronology: tree-ring analysis of recovered oak timbers showed the wood was felled between 1626 to 1639. A 5-person team of commercial divers and maritime archaeologists then compressed their work into 22 dives over a little more than 12 days, racing to document and recover material before dredging resumed, according to 1626 to 1639 reporting.

Led by Michał Grabowski of the University of Warsaw, the rescue excavation logged more than 60 artifacts, including shoe soles, rope, pulley blocks, an anchor, and barrel staves. One standout was a hollowed-out oak trunk about 11.8 feet long, thought to be the ship’s bilge pump. Grabowski also pointed to carpentry tools, including a hand-drill brace handle he said “closely resembles examples recovered from the Mary Rose shipwreck,” hinting at an onboard repair workshop.

The brick that won’t give up its secret

Then there’s the object that keeps this from feeling like a tidy catalog: a flat, yellowish clay brick about 5 by 3 inches, pierced by 4 or 5 cone-shaped holes, fitted tightly into an oak block. “I had no idea what it was, but I really wanted to solve the mystery,” Grabowski said. His preliminary hypothesis is practical, that it may have been an improvised sharpening device for drill bits or chisels, but he added: “To date, no direct parallels or definitive explanation of the object’s function have been identified.”

Protection now, bigger questions later

What do you do when industrial timelines collide with a 400-year-old hull? In this case, the pipeline route was rerouted around the site, and divers covered the remains with sandbags. A follow-up inspection dive in 2024 found the wreck still safely buried, while Grabowski’s preliminary report appeared in the International Journal of Nautical Archaeology in 2026, alongside wider attention to the clinker-built hull. The ship’s name, home port, destination, and cargo remain unknown, but the mystery brick is now part of the record, waiting for its match in history.