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The Unexploded Bomb That Never Would

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During the Second World War, the British coastline was littered with ordnance, much of which did not explode. Although mine clearing efforts after the war got rid of much of the unspent ammunition, some inevitably slipped through the net. Atlantic Scuba's Mark Milburn recounts the story of finding an unexploded device that turned out to be unexpectedly different

While diving around Falmouth Bay recently, looking for the lost 1916 HM Trawler St Ives, I came across what I thought was a possible bomb, around 1km offshore at a depth of between 14-17m, depending on the tide.I had seen a similar device before, which I had reported to the Explosive Ordnance Disposal Unit (EODU), who subsequently destroyed it.   

On surfacing, we stored the coordinates, but there was no way of acquiring an exact position without attaching something to the device, with a straight line to the surface. I returned with some volunteer divers, to help relocate the suspected bomb. We filmed, photographed and measured it so that the images could be shown to the EODU in the hope it could be identified. 

Weather conditions were not ideal for a while, but as soon as there was a hole in the weather, a small group of us went out on my boat. We dropped into the choppy sea and descended to look for the object. The device took a while to relocate, due to the poor in-water visibility from the recent weather and the very rough original coordinates. Once relocated, the remaining dive time had been considerably shortened, the visibility wasn't great and the surface conditions were worsening. The dive was called off – we would have to return. 

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Measuring the unexploded parachute mine (Photo: Mark Milburn / Atlantic Scuba)

A few days later, the weather forecast gave us another chance to return. On arrival at the site, the surface conditions were greatly improved compared to our last visit. I jumped in with my buddy for the day, Sue Barnes, then descended to the seabed. Within five minutes we were on the device, where we photographed and filmed the object before I marked the site with a buoy. After the dive, the second buddy pair of David Gibbins and Katrina Mace went down, to take even more photographs. After the dives, we discussed what we had seen. We all believed it was highly probable that it was a parachute mine, possibly a type GC with its end cap still in place. We arrived back on shore late that evening, so waited until the following morning to contact the authorities. 

Early on Wednesday morning, I called the Maritime and Coastguard Agency (MCA), who requested some photographs (of which we had many), and then passed them onto the EODU. On seeing the images, the EODU rang me and stated that it needed looking at, to see if it was indeed a potentially dangerous device. They were loading up and would be down within two hours. 

The EODU arrived at Maenporth Beach, the closest place the device to launch their boat. Their divers went in, and we all waited to find out what the device was. Time passed slowly on that cold afternoon. Eventually, the EODU diver surfaced, and when the boat returned, the commanding officer told us that it was, in fact, a parachute mine, type GC. There was not enough daylight to continue with a disposal, they would have to return the following morning. 

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EODU divers preparing to inspect the unexploded bomb (Photo: Mark Milburn / Atlantic Scuba)

On Thursday morning, the EODU left Falmouth on their boat, followed by the RNLI, the harbour master and the harbour pilot. The EODU sent a diver down, while the other boats kept all their vessels at bay. On the shore at Maenporth, several dozen people waited patiently for the detonation. The EODU's boat moved away. A small column of water shot up, followed a few seconds later by a short bang. Everyone looked at each other. 'Was that it?” was the question heard echoing among the onlookers.

Surely not? Compared to the last detonation five years ago, this was a bit of a damp squib. Everyone kept watching and recording. The EODU diver descended to inspect the results, and fifteen minutes later, all the boats were off, and that was it. The MCA told us that the EODU had declared that the device was now safe. 

Bemused by the events, we discussed what had happened. We could only assume that the mine had come down so fast, without its parachute deploying, that it damaged the internal workings and cracked the watertight casing. Seventy-five years of salt water ingress may have caused the explosives to be harmless. 

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The dampest of squibs (Photo: Mark Milburn / Atlantic Scuba)

From the first time I had spotted the device, I hadn't been 100 per cent certain what it was. I had seen a parachute mine type GC before and this one had looked very similar, but I couldn't work out what was different about it. I assumed at the time that it was because it was in deeper water and the seaweed covering was more dense.

When the previous mine I had found was detonated by the EODU, they had told me it was most probably live, and when it was blown up, it certainly looked more 'live' than the damp squib we had just witnessed. There was something about this new discovery, however, which made me feel that it wasn't quite right.

The following day, I dragged my divers back out to the site and found that my shot line had disappeared, either blown up or removed by the EODU, so I dropped another and headed back down to the remains of the bomb, but what I found there was rather confusing.

What I saw was made of concrete, with a nose area full of iron and steel pieces, with a bar through the centre and circular plates along its length. Had all this fuss been over a lump of concrete? Finding that this was the case was disappointing, but David sent me a link to a story that might explain our discovery.

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The remains of the mine after 'detonation' - the concrete nose is to the left of the picture (Photo: Mark Milburn / Atlantic Scuba)

During the Second World War, a shortage of explosives led to a shortage of mines, and so replicas were made from concrete and dropped in their place. They might not have destroyed anything, but what they did do was back up the shipping while the fake mines were cleared, and where the waiting ships would be easy targets. According to the story, both sides had resorted to this tactic, so we started wondering if what we had found could have been a fake bomb dropped by a German aircraft.

A few days later, David, Jan and I returned once more to dive the site of the now destroyed 'bomb'. We found nuts and bolts, steel springs, chains and - rather bizarrely - a glass candlestick holder. Some of the items dated as far back as 1910, which you might expect from a 1940s scrap heap. All of this scrap was packed into the remains of the concrete nose, which would have caused the fake to fall nose-first like a genuine bomb. 

The steel bar and discs were clearly cut in metric measurements – implying the bomb was of German origin, as the British were still using imperial measurements at the time – but the pieces were roughly cut, as opposed to the genuine mines which were well-made and constructed from aluminium. The remains of black paint on what was left of the casing indicated an attempt to make the fake bomb look realistic.

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The concrete nose packed with scrap metal (Photo: Mark Milburn / Atlantic Scuba)

It had fooled the British during the Second World War - and it had fooled us again more than 75 years later.

We know that the Falmouth area was extensively mined during the Second World War, so much so that the number of ships lost to the mines meant that in 1940m the port had to be closed several times while the explosives were cleared.

The fake mine that we discovered was the first one we know of that has been found and identified in the area, probably because it was outside of the normal shipping routes and therefore missed by the clearing operations, rather like the real one I found in the mouth of the Helford five years ago - but that's another story....

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Nuts and bolts and springs (L) and the glass candlestick holder (R) (Photo: Mark Milburn / Atlantic Scuba)

We'd love to hear your diving stories. If you think others might learn from your experience, or if you've just got a fishy tale to tell – and if you'd like to see your story featured on our website and in the DIVELive app and weekly digest – why not drop us a line at This email address is being protected from spambots. You need JavaScript enabled to view it.



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