There was a lot of stuff dumped in the NW approaches Ninja. If trawlers are working in the area its inevitable that some of its going to be trawled up. I know there was a lot of ordinance, phosphorus etc dumped in the Beaufort dyke (not a lesbian) and it sometimes came ashore in South West Scotland and the NI coast. My only experience of anything like it was SW of Barra. we trawled up a WW2 torpedo. It wasn't intentional and we collectivity shat ourselves.
None of it is deliberate on any side. Where you have trawling and Submarine ops in confined waters there are going to be accidents. Just have to minimise them where possible. The Sub Fax broadcasts help, but if you have a Boat stalking a ruski you cant be expected to broadcast its position.