Dorado sailed from New London 6 October 1943, for the Canal Zone but never arrived. Air searches were begun immediately after her scheduled date of arrival 14 October. Widely scattered oil slicks with occasional debris were found and later investigation revealed that a patrol plane from Guantanamo Bay delivered a surprise attack on an unidentified submarine on 12 October and was later fired upon by another unidentified submarine. A German submarine was known to be operating near the scene of these two contacts, but the actual fate of Dorado remains unknown.