Swimming has been part of at every Summer Paralympic Games.
Races are held in four swimming strokes: freestyle, backstroke, breaststroke and butterfly over varying distances and in either individual or relay race events.
Medley events combine all four strokes, again either as an individual format (swum in order: butterfly, backstroke, breaststroke, freestyle) and as a team relay (swim in order: backstroke, breaststroke, butterfly, freestyle).
The decision is made by the IPC based on factors including there being a minimum of 6 athletes from a minimum of 4 National Paralympic Committees to make a race viable.
In addition, an event must have been also held at the previous Games, or at the IPC Swimming World Championships held between the Games.