Here's a bombshell of a discovery.

Brooklyn commercial divers believe they've uncovered what the Navy missed more than 50 years ago during a frantic search that made national headlines: roughly 1,500 live shells that went overboard into the Narrows and Gravesend Bay.

The Post joined the four-person crew last week searching for artifacts in the murky waters off the former Fort Lafayette -- an island near Bay Ridge destroyed in 1960 to pave the way for the Verrazano-Narrows Bridge....