"UNREP" (short for "underway replenishment") is the term used to describe the transfer of fuel, food, ammunition, repair or replacement parts, people and mail from supply ships to combatants like frigates, destroyers, and aircraft carriers. Simply put, UNREP keeps Navy ships at sea. It's a dangerous and intense evolution.
Here are 18 photos that show the intensity of keeping warships supplied at sea
UNREP begins by raising the Romeo flag. On the control ship, it means, "I am ready for your approach." On the approaching ship, it means, "I am commencing."
One of the most challenging aspects of UNREP is matching the speed of the control ship and steering into position.
Once the ships are on a parallel course, a shotline is sent for the phone and distance (PD) line, which is marked by flags every 20 feet. Once the shotline is fired, sailors on the supply ship catch it like a wedding bouquet.
After the shotline is received, line handlers must haul in the messenger line, which is much heavier.
After the wires and hoses are connected, the teams on deck and in the pump room are ready to begin the transfer of cargo and fuel.
Sailors in the pump room monitor fuel levels...
... while pallets of food, mail, and supplies are transferred topside.
At the same time sailors man the .50 cals, ever-vigilant for threats.
Thousands of pounds of fuel and cargo are transferred between the ships while maintaining the same speed and distance apart.
The exchange can be dangerous for both sides...
Sailors have to watch out for rogue waves.
Helicopters can also be used for resupply ...
They call this process "VERTREP," short for "vertical replenishment."
Resupplying the ship is an all-hands task. In this photo, sailors and Marines on an amphibious ship form a human chain to transfer packages.
Sometimes ships will tag-team a supply ship to save time. In this photo, two missile destroyers -- an Arleigh Burke class and a Ticonderoga class -- are attached to the USNS Lenthall (T-AO 189).
Sometimes an UNREP could go well into evening...
... and package distribution could go on for hours after the ships have disconnected.
But, the long hours and hard work pay off when you receive a care package from home; it's like Christmas.
Read more on WATM: