About the water part: Historically you are completely right, but with the crazy amount of global shipping in the 21st century, I think lots of sea impacts would

About the water part: Historically you are completely right, but with the crazy amount of global shipping in the 21st century, I think lots of sea impacts would be detected and/or sink a couple of ships. Take a look at vessel finder and you'll see that there are only a few areas where ships are really far apart.