I had a marine biology professor that told us of the time he assisted with the cleanup of a coastal estuary somewhere near Morro Bay, CA. The area had been used for coastal target practice for years and had been off limits since around the Korean War.
He had assisted in the cleanup of old munitions for some time before the area was declared safe. Shortly after that he led a group of elementary school kids on a tour of the estuary. As part of this, he described what had been done and what had been removed to make the place safe.
Then a kid asked,"Like this?" While she pulled a live mortar shell out of the sand.
My professor said he didn't change his tone, just said "Yes! Just like that. Now just set it down and let's head back to the busses"
He commented that the area was swept a few more times before it was reppened.