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Danger UXO (UneXploded Ordnance)

Simon Brown on the mysterious and possibly dangerous metal tubes which can be found in the waters off Dorset

An anti-submarine mortar round, known as a hedgehog

Portland has a long naval history and, although the naval base closed in 1995, the evidence of naval warfare has an omnipresence that persists today. Buildings, underground bunkers and pillboxes on the shore are daily reminders, but smaller but more potent reminders litter the seabed. It takes some clever sonar to detect their presence, they tend to appear as small, shadowy, straight-edged targets on a ghostly image on the screen. By sonar alone, depth charges and torpedoes often look like iron cannon, a weapon dating from the age of sail rather than modern warfare, so the only way to verify what the object might be is to dive, search and identify.
One of the first targets we dived turned out to be unexploded ordnance rather than the hoped-for cannon. As my eyes adjusted to the gloomy underwater world, a long cylindrical object came into view: a 21-inch torpedo with the propeller end buried in the seabed minus its warhead. Lying close by was the warhead… with a very large lobster occupying the space normally occupied by 500lbs of high explosive. This torpedo was inert. The next dive turned up an object no one could identify, but everyone agreed was ‘nasty looking’ and guessed ‘depth charge’. A rusting steel tube about eight feet long and 18 inches in diameter, blanked at both ends and very rusty, was lying on the seabed. A quick seabed search revealed another two identical objects. The locations were reported to the authorities, and were later confirmed as airdropped anti-submarine depth charges but all proved to be inert.
Anti-submarine weapons are the most common find, and perhaps this should not be a surprise with the Admiralty Underwater Weapons Establishment based on Portland. Testing with inert weapons for hydrodynamic performance is always inherently safer than using live ordnance, so using a dummy weapon makes a lot of sense.

A diver photographs two anti-submarine mortar rounds, known as squid

From the sonar view, manmade objects stand out like the proverbial sore thumb. Whilst the hunt for evidence of the Battle of Portland – where the Dutch and English navies of the day fought for three days in 1653 – continues, munitions from the modern age will be found; after all, a long, cylindrical underwater weapon looks very much like an iron cannon. A dive is always needed to check, and one never quite knows what will be on the end of the anchor line.

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