NORTH KINGSTOWN, R.I. -- Officials representing the Navy and shipbuilders gathered with politicians Monday to praise a $2.5 billion submarine that they say will be the stealthiest vessel patrolling the oceans for the U.S. military — the South Dakota. It will have quieter machinery, a coating on its hull to further eliminate noise and sonar panels to better detect and track other submarines, Rear Adm. Michael Jabaley said during the ceremony in Rhode Island, where the submarine is being built. Those new modifications represent about $115 million of the cost, the Navy says. "With the undersea environment constantly changing and becoming more crowded with capable threats, the Navy has decided to use South Dakota as a prototype ship that will include significant investments in stealth beyond anything seen to date," Jabaley said. The ceremony, which formally marked construction of the nation's 17th Virginia-class attack submarine, was held at a manufacturing plant operated by Electric Boat, a subsidiary of General Dynamics. Groton, Connecticut-based Electric Boat and Newport News Shipbuilding in Virginia are building the South Dakota. They have an agreement to build two Virginia-class attack submarines annually. Construction on the South Dakota began in March 2013, and the submarine is 65 percent complete. Its contracted delivery date is August 2018. In keeping with Navy tradition, the ship's sponsor, Deanie Dempsey, wrote her initials on a metal plate that will be mounted on the submarine. A welder traced over her initials to make them permanent. Dempsey, the wife of former Joint Chiefs of Staff chairman and retired U.S. Army Gen. Martin Dempsey, is an advocate for military families and volunteers with military support organizations. "I am beyond honored and thrilled to be here and to start this relationship with all of you," she said at the ceremony. Martin Dempsey, who was in the audience, said he loved the tradition of the keel-laying ceremony and the "heartfelt passion" for building submarines that it showcased. "The merging of men and machines is really remarkable," he said. Members of Congress from Rhode Island, Connecticut and South Dakota spoke about the nation's need for submarines. They, along with Rhode Island Gov. Gina Raimondo, a Democrat, thanked the shipbuilders and service members in attendance. U.S. Sen. Mike Rounds, a South Dakota Republican, said "a new symbolic link" is now formed between South Dakota and the Navy.