I found a Colt 1911 just off a bridge in Narragansett, RI. I would dive the waters under the bridge once or twice per summer. I got a big hit in the deepest part of the river (about 12' deep) just below where kids would jump off the bridge. I got a big hit near a large flat rock and started fanning on the backside of the rock. Turned up a watch, two rings, and a slightly rusted .45. I tied a float to the rock, swam to shore and had someone call the police department. Their dive team showed up about 20 mins later went and pulled out the pistol... then asked me if they could borrow my detector to search the area again....
I was hoping that I'd be able to reclaim the pistol... but when I called back they told me it was "evidence". Although, I think one of the officers really liked it...