A sunken German U-boat dating back to The First World War has been discovered off the coast of England during a scan of the seabed for windfarm development.

The German submarine, which had been missing in action for more than a century, was found during a detailed scan undertaken by developers Vattenfall and ScottishPower Renewables (SPR). According to a press release from SPR, the team expected to find wrecks during the survey, but not an uncharted one from 1915; East Anglia ONE windfarm project director Charlie Jordan says it was quite surprising – as well as intensely interesting – to make the unexpected discovery.

Using highly advanced sonar technologies to scan more than 6,000 square kilometers over the course of two years, SPR and Vattenfall undertook the operation to gain critical understanding of the seafloor in order to lay their windfarm project out effectively. Upwards of 60 wrecks were catalogued during the two-year scan, but the lion’s share of these were expected to be found. The uncharted U-boat, found just 90 kilometers offshore, was one of the few surprises the scanning team stumbled upon.