Large harbor tug Opelika (YTB 798) and Kittanning (YTB 787) follow alongside the Arleigh Burke-class guided missile destroyer USS Mustin (DDG 89) as she gets underway on board Commander Fleet Activities Yokosuka. U.S. The U.S. Navy large harbor tugs seem to have all but disappeared from most U.S. ports over the last decade. But in a few ports around the world the Navy-owned and operated tug endures as the backbone of port operations. Fleet Activities Yokosuka happens to be one of the naval bases on which the legacy of the large harbor tug continues to influence not only the operations of the port, but the Sailors that work aboard these perennial workhorses of the Navy.