The army were called and became concerned about the object when it was described as ‘smoking’. They then ordered in the nearest EOD unit, a Royal Navy bomb disposal team.
It is unusual for unexploded ordnance (UXO) of this age (>75 years) to begin emitting smoke. Especially a device that has been submerged in the sea for decades.
An incendiary device?
The weapon was subsequently blown up by the EOD team on the beach. A video of this controlled detonation features an intense flame shooting out to sea. This suggests an incendiary composition, as opposed to purely high explosive.
The item was described as 10 inches long, however its precise identity was not confirmed by the Royal Navy. It could have been a phosphorus incendiary device. Munitions-quality white phosphorus reacts violently when it comes into contact with oxygen in the air. It spontaneously ignites producing a very hazardous effect. The smoke could have been due to a crack in the item’s casing, allowing some air in.
This could have been a training aid / battle simulant used during WW2 military exercises in the area, see below. Alternatively, the device could have been a German B2.2EZ incendiary bomb. This weapon had a body length of 9.25 inches and included a small high explosive charge.
Allied commanders devised a large scale amphibious landing exercise in the spring of 1944. It took place at Slapton Sands between 22nd and 30th April and involved 30,000+ troops.
To simulate battle conditions, there was a naval bombardment onto the beach just prior to the landing. Following this, ammunition was fired seaward from forces inland, over the heads of the assault troops. Live ammunition was used during both. Inevitably some items failed to function, creating a legacy of UXO. Smoke grenades and flash simulants were also used.
UXO has been continually encountered in the area since WW2. In 2018, Storm Emma uncovered various items, including an American anti-tank mine.
The unique combination of the sea (water currents) and much historic military activity, concentrates UXO at coastlines. Naval weapons such as mines and shells frequently wash up on shores around the world. And this is in addition to land-based military activity resulting in UXO contamination.