The member of the public found what they believed was an unexploded bomb in the River Nidd at Knaresborough on May 16.
Yet they retrieved the object and took it back home with them before calling 999.
Police had to erect a 100-metre cordon around their house while an army bomb disposal team removed the item and dealt with it.
It has not been confirmed whether the item was actually dangerous.
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North Yorkshire Police said: “If you come across something that you think may be an explosive device such a bomb, shell, mortar or marine flare for example:-
• Leave the item where it is – even if it looks old and rusty, it may still contain explosives and is therefore potentially dangerous
• Move at least 50m away and call the Police on 101 and give them clear information about the location of the suspect item.
“If you don’t know the postal address, provide the police with details of local landmarks. Or if you have What3Words on your phone it would be helpful to give the police the precise location.
“If you are able to you could provide a description of the item, including any markings that may be on it. The police will make contact with the Explosives Ordnance Disposal Officer (bomb disposal officer), who will be able to take the necessary action.
“Thankfully the EOD were able to dispose of the object, and the incident was brought to a safe conclusion.
“Our thanks to residents in the local area for their patience whilst we dealt with the incident.”