I don't know about the WWII case, but in countries like the UK where it is legal to be buried at sea there are regulations about where you can perform the ceremony specifically because bodies do drift: https://www.bbc.com/news/world-europe-guernsey-24224570

Although the article mentions that this is the first time it's happened in 25 years, note that only about a dozen people every year choose to be buried in this way: https://www.bbc.com/news/uk-england-38210497