chaired by the president of World Aquatics. Between Congress meetings of the entire membership, a smaller 22-member representative board, called the World Aquatics Bureau, meets to act in a timely manner on items which cannot wait until the entire body can meet. It is the Bureau that elects World Aquatics' Executive Officers. Various committees and commission also help with the oversight of individual disciplines (e.g. the Technical Open Water Swimming Committee helps with open water), or topic-related issues (e.g. the World Aquatics Doping Panel). Presidents Each presidential term is four years, beginning and concluding with the year following the Summer Olympics. Events World Aquatics Championships World Aquatics' biggest event is the biennial World Aquatics Championships, held every odd year, where all of the six aquatic disciplines are contested. A 50m length pool is used for swimming races. The World Open Water Swimming Championships (a.k.a. "Open Water Worlds") is part of the World Aquatics Championships. Additional standalone editions of the Open Water Championships were also held in the even years from 2000 to 2010. The World Masters Championships (a.k.a. "Masters Worlds") – open to athletes 25 years and above in each aquatics discipline (30+ years in water polo) – has been held as part of the World Aquatics Championships since 2015. Prior to this, the Masters Championship was held separately, biennially in even years. The World Aquatics Championship has been held biennially since 2001. Between 1978 and 1998, the World Aquatics Championship was held every 4 years, in the even year between Summer Olympic Games. Stand-alone discipline competitions World Aquatics also organizes separate tournaments and series for individual disciplines, including competitions for juniors. Discipline world tournaments Swimming: World Swimming Championships (25m), (a.k.a. "Short Course Worlds", an even-years biennial event, in 25m length pool) Water polo: Men's and Women's Water Polo World Cup, replacing the former Water Polo World Leagues Diving: Diving World Cup (biennial) High diving: High Diving World Cup (annual) Discipline world series Swimming: Swimming World Cup (annual, in 25m pools) Diving: Diving World Series (annual) Artistic swimming: Artistic Swimming World Cup (annual - called World Series 2017-2022) Open water swimming: Marathon Swim World Series (annual) Junior championships World-level championships restricted to a younger age, with the age limit varying by discipline and gender: Swimming: World Junior Swimming Championships (biennial) Water polo: Junior and Youth Water Polo World Championships (biennial) Diving: World Junior Diving Championships (biennial) Artistic swimming: World Junior