SpaceX has acquired two former oil drilling rigs to serve as these floating spaceports. Named Phobos and Deimos, after the two moons of Mars, they are currently undergoing modifications to support Starship launch operations.
SpaceX has long been hinting at future floating launch and landing sites for their Starship launch system. The super heavy lift launch vehicle will have a large blast danger area and pose noise concerns if launched frequently near populated areas. Therefore, sea launch platforms will play a key role in the launch cadence SpaceX plans to reach with Starship, including on-orbit refueling flights for deep space missions and transportation from one place to another on Earth.