A crew member dressed as Santa rides atop the hull as the Virginia-class attack submarine PCU South Dakota (SSN 790) transits the Thames River off Groton en route to the U.S. Navy Submarine Base in Groton Thursday, December 20, 2018 after a month out on Sea Trials. The South Dakota, which carries the Pre-Commissioning Unit designation instead of USS until commissioning in February of 2019, is the 17th boat in the class, the seventh in the Block III design series. (Sean D. Elliot/The Day)