The essential point which was not made at the time is that the Western Approaches of the North Atlantic are a graveyard of millions of tons of ships lost through natural and unnatural causes. During 1942/43 alone about 12 million tons of merchant vessels were sunk along with a considerable number of naval ships, U-boats and aircraft. As far as we can tell no one has suffered any subsequent harm, despite the fact that those ships carried practically every form of man-made substances and artefacts.
Pull the plug, note the Navsat readings, then forget it.
G A HENWOOD