HM Coastguard said the torpedo was found on the seabed during an underwater salvage sites survey. This survey is regularly carried out in the harbour. Its primary aim is to assess the condition of the many German warships that were scuttled in the anchorage on 21st June 1919.
The British weapon was found close to the site of another torpedo find, which occurred in 2016. The first was German and is thought to have been fired by the U-Boat that sunk HMS Royal Oak during WW2.
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An exclusion zone of 500m was set up around the scene in the Orkney Islands, Scotland. A Royal Navy team of divers then destroyed the weapon in a controlled explosion. The same method of disposal was used for the German torpedo.
Does this find pose a significant hazard?
The large radius of the exclusion zone gives an indication of the hazard. Torpedoes contain some of the largest high explosive warheads of any weapon type. They were, after all, designed to sink warships weighing 40,000 tons.
The sonar survey found the torpedo in 100ft of water. It was in pieces and heavily rusted, with the presence of white material indicating it was still live and viable. However, such a device will only pose a threat if it is disturbed. There is an extremely low likelihood of such a weapon inadvertently detonating.
The Royal Navy divers identified it as a Mk VIII British torpedo. This model measured 6.6m in length and could carry a 365kg TNT warhead to a distance of 4.5km. It was widely used by the Royal Navy and allied navies during WW2.
The UK coastline is littered with a wide variety of unexploded ordnance (UXO). UXO contamination is concentrated in shallow tidal waters for a number of reasons relating to historic conflicts, weapons ranges, coastal defences and marine currents.