They are semi-submersible heavy lift ships, which is to say that the ships are designed to be ballasted down so that their main decks go underwater, allowing their cargo to be floated aboard.

FORBES: Will the Vanguard Semi-Submersible Ultra Heavy Lift Ship Keep Dockwise Afloat?

Welcome aboard Air Force One as we make our way north to Northern California, San Francisco, before we go to Denver.

WHITEHOUSE: The White House