The Cambodian Water Festival (variously spelled in the original Khmer as Bon Om Touk, or Bon Om Thook, or Bonn Om Teuk, or Bon Om Tuk) takes place once a year, on the full moon of the Buddhist month of Kadeuk (usually in November). It celebrates a major natural occurrence: the reversing flow between the Tonle Sap and the Mekong River.