The U.S. Navy is continuing to expand use of its "Sea Swap" program, by assigning several crews to each of their new Littoral Combat Ships (LCS). The original idea behind Sea Swap was to eliminate the transit time, which can be up to a month, as the warship makes its way out to a far away area (like the Persian Gulf), for a six month tour. With Sea Swap, the ship stays out there for 18-24 months, while the crews do their usual six months at sea before flying home. The LCS is meant for operations along the coast. The LCS type ships (there are two designs at the moment) displace about 2,500 tons, with a full load draft of under ten feet, permitting access to very shallow water, as in coastal and riverine waters, where most naval operations have taken place in the past generation. Top speed is over 80 kilometers, with a range of 2,700 kilometers. Built using commercial "smartship" technologies, which greatly reduce personnel requirements, the basic LCS is expected to require a crew of about 50 in basic configuration, but will have billeting for about 75 personnel. The ship is designed for a variety of interchangeable modules (e.g., air defense, underwater warfare, special operations, surface attack, etc.), which will allow the ships to be quickly reconfigured for various specialized missions. Crews will also be modularized, so that specialized teams can be swapped in to operate specific modules.
Multiple crews for the LCS will allow these ships to stay at sea constantly, without wearing out the crews. This would mean that, for interdiction operations, where suspicious ships are boarded and searched, you can wear the crews out real quick, without putting a lot of stress on the ships. Multiple crews allows you to keep the sailors rested, and not worn out.
One of the problems with ships operating continually, was that they suffered more wear and tear, and required more work from the crew to keep everything operational. In the past, ships would come back after a six month tour and spend a lot of time in port, where maintenance was done. New ships are going to have design features that can better handle the longer times at sea.
The Sea Swap crews, since they are kept together as they rotate through several ships of the same class, have taken to naming themselves after their home ship. Thus you have Team Spruance, that would only get to serve on the USS Spruance one third of the time (six months every 18 months).
The concept of multiple crews is nothing new. Ballistic missile submarines have been doing it (using two crews to maximize the time the subs can stay at sea) for two generations. And the air wings (several thousand sailors and pilots strong each) that operate off carriers, have also been going from one carrier to another, with shore assignments in between, for many decades. Multiple crews were also used with the coastal patrol boats the navy built in the 1990s, and now uses in the Persian Gulf.