The hedgehog was fired from the bow of a destroyer. It was effectively a forward firing mortar and allowed the destroyer to maintain ASDIC contact with the U-boat when firing the weapon thus making it more accurate than the depth charge. I believe it was introduced around 1942/43. So what you are seeing is not the hedgehog.
Nemo
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"I'm afraid there is no disguising the fact that King's obsession with the Pacific and the Battle of Washington cost us dear in the Battle of the Atlantic".
Sir John Slessor GCB, DSO, MC, DL
AOC-in-C Coastal Command RAF
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