When I was a kid, my parents had a beach place.
That beach used to be a military training ground during WW1 and WW2.
The military removed all of the ordinance and the property was put up for sale in the 1950's.
My friends and I made a hobby out of collecting .50 cal bullet fragments and rusty bomb shells.
One day we pulled a conical shell out of 12 feet of water and chipped the concretion off of it with a hammer and screwdriver, cleaned it up, and took it to school the next day for show and tell.
Then the police showed up at the school and called the bomb squad, who discovered live powder in the shell and detonated it at the local military base.
Awhile later the navy conducted some "underwater training exercises" near my parents' beach place and recovered some unidentifiable (to me anyway) objects.
I don't play with fireworks anymore.