The English Channel. People have been crossing the channel since the dawn of man. I think if one could recover every man made item on the bottom of the channel you'd need a small country to house the museum.
I don't think the plane in which Glenn Miller died (Famous big Band Leader) was ever found, right? There reports that it 'may' have been found back in 2019 but I have never seen a confirmation and if it had been found, for sure, that would be major news.
