In 1991, a Lake Michigan fishing vessel crew netted an object they later deposited on a beach in Sheboygan, Wisconsin. It was subsequently identified as a fully-armed Sidewinder missile. While this is an extreme example of unexploded ordnance (UXO) pollution, it highlights the issue of old military munitions in the Great Lakes.
Great Lakes Now
https://www.greatlakesnow.org/2021/01/unexploded-ordnance-lake-erie-shoreline-site-munitions-study/