The only nuclear submarine ever to sink an enemy warship, she was paid off and laid up in 1990.

Sheean is the only submarine named after an enlisted sailor.

She was the only German submarine commissioned with the number 115.

The only submarines which could have hit the Saudi oil installations.

She is the only submarine known to have been sunk by a battleship.

The only submarine of the class built to the original Project 627 design.

We are the only submarine that should be in the area.

She was the only German submarine to be sunk by land-based artillery fire during the war.

Holland 5 remains the only submarine of her class on the seabed.

Rover was the only submarine in her class to survive the war-the others were all sunk by 1943.