On maneuvers in unfriendly waters of when it just isn't practical to stop what ever you are doing and to head to port to buy fuel war ships fuel at sea.
It is a complex arrangement. First a small line is passed from the ship in need of fuel to the refueller. Once that is done the line is tied on the a heavier line then attached to a steel cable which is attached to both ships. That cable is kept taut using a winch system on the fueller. Once the steel cable is secure the fuel line is strung across and once attached the fueller will begin to pump fuel across.
Always a little exciting
|HMCS Fraser approaching the refuler|
|HMCS Provider.(Note the sailor in the wet suit standing by in case someone went over the side)|
|HMCS Provider refueling HMCS St Croix|