By the 21st century, the Moon has been colonized, and although still very much a research establishment, it is visited by tourists who can afford the trip. One of its attractions is a cruise across one of the lunar seas, named the Sea of Thirst, (located within the Sinus Roris) filled with an extremely fine dust, a fine powder far drier than the contents of a terrestrial desert and which almost flows like water, instead of the common regolith which covers most of the lunar surface. A specially designed "boat" named the Selene skims over the surface of the dust in the same manner as a jetski.