This.... was more in the paper so from memory.
Local newspaper had front page news this week of how the police were called to the Central Junior School as one of the pupils had taken in an unexploded WW2 shell for show and tell....
Apparently her Dad had found it and five friends whilst diving in Swansea bay over the last week. Police / bomb squad go in search of other 5 only to find he has dumped them in a rubbish bin - which has been emptied. Now a frantic search is on for 5 shells somewhere in the local refuse system.

Maybe the water leaked into his head whilst diving?
R