Well, you'll be glad to know that people like my dad (ATO/EOD) sorted quite a lot of it out back in the day. However, they could only demolish what they were pointed at and as this article notes, there is more that keeps on turning up.
This is a bit of a worry: https://en.wikipedia.org/wiki/SS_Richard_Montgomery
I suggest you don't buy property or go swimming nearby to that. I'm going to stick in Somerset.