Police sealed off an area around Portsmouth Harbour after an unexploded torpedo was found in Portsmouth Harbour this morning.
The port was closed to all vessels at 5am while the Royal Navy towed the wartime device out of the harbour to carry out a controlled explosion out at sea.
Train and ferry services were cancelled during the investigation.
Wightlink Ferries said in a statement: "The 06:00 car ferry sailing from Portsmouth Gunwharf and 07:00 from Fishbourne were cancelled along with the 06.15 catamaran from Portsmouth Harbour and 06.47 from Ryde Pier Head.
"The port re-opened at 06.25 and services have now resumed as normal with the delayed 07.00 St Clare sailing from Portsmouth Gunwharf. Wightlink apologises for this delay to its sailings this morning".
After the end of World War II, it was revealed that the Mark 14 torpedos used by the US navy until 1942 were notoriously unreliable. Out of 1,442 torpedoes fired in the Pacific theatre, only 109 ships were sunk.
The torpedoes would frequently run to deep, missing targets, fail to explode, or run in a circle and strike the submarine they were fired from.
There are no figures available for the total number of unexploded torpedoes in seas and oceans.