PUBLISHED: 09:48, Wed, Oct 7, 2020 | UPDATED: 09:49, Wed, Oct 7, 2020
The discovery came as a total surprise to a team of Polish archaeologists exploring the lake for much older artefacts. Lake Hammerso is the largest reservoir of water on the small island of Bornholm in the Baltic Sea, just south of Sweden. According to ancient traditions practised by the island's residents some 1,500 to 2,500 years ago, weapons taken from invaders would be ceremonially dumped into the island's lakes.
Lake Hammerso in the northeast corner of the island and near the ruins of Castle Hammershus seemed like the perfect candidate to find some of these weapons.
Professor Bartosz Kontny from the University of Warsaw's Department of Archaeology said: "The people living in Scandinavia 1,500 to 2,500 years ago practised the ritual destruction of weapons captured from invaders.
"The weapons were then thrown into the lakes during ceremonies."
The archaeologists led an expedition to Lake Hammerso this September, sending divers into the shallow waters.
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Archaeology news: The artefacts were pulled from Lake Hammerson on the island of Bornholm (Image: BARTOSZ KONTNY)
But rather than finding ancient treasures and weaponry, the archaeologists were greeted with a great deal of rubbish.
The bottom of the lake was littered with bottles, cans, coins and metal rods - likely from a nearby quarry.
And at the centre of Hammerso, they uncovered a modern-day bathtub, which they initially confused for a dugout canoe.
Professor Kontny: "At first we thought it was