Zumwalt-class destroyer USS Lyndon B. Johnson launched in Maine

The process involves moving the vessel to a dry dock after construction and slowly pumping water into it before starting final work on the ship.

"It's important for the DDG 1000 program and shipyard to reach this major milestone," Capt. Kevin Smith, DDG 1000 program manager for the Navy, said in a press release.

"With the first two ships of the class underway, we are excited to continue the next phase of construction of the future Lyndon B. Johnson," Smith said

The ship is expected to be christened in 2019 and enter active service in 2021, along with the Zumwalt and Michael Monsoor, the other two ships of the Zumwalt-class.

The Zumwalt-class is supposed to be the most advanced destroyer ever built, with stealth technology and a gun system that could provide precision fire support for amphibious forces.

It is billed to having a electrical propulsion system that can manage future power heavy systems such as lasers. For a surface combatant, it is large, at nearly 15,000 tons, making it the heaviest in its class built by the United States.

The gun system has been left as an option due to the cost of the round designed for it. The Navy has said in multiple Congressional hearings and statements that they will wait for relevant technology or remove it for space.