What may a swimmer not do during a race?

• The distance: "An Athlete must complete the course distance (or, in a relay, their quarter of the total race distance)."
• The lane: an athlete "must start the race in his/her allocated lane, remain in that lane throughout the race, and finish the race in that lane".
• The wall: at a turn the athlete must make physical contact with the wall and must not take a stride or step from the bottom.
• The bottom: "An Athlete must not stand and/or walk on the pool bottom". The exception is standing during freestyle events and the freestyle part of medley events.
• The lane rope: "An Athlete must not pull on the lane rope."
• Other swimmers: "An Athlete must not obstruct or otherwise interfere with another Athlete."
• Getting out: a swimmer who has finished must leave the pool as soon as possible without interfering with anyone still racing.
• Jumping in: an athlete who is not in a race must not enter the water during it, or before everyone in it has finished.
• The penalty: the referee disqualifies the athlete from that event. For entering the water during someone else's race, the athlete is disqualified from the next race they are due to swim.
• The victim: if a breach has harmed another swimmer's chances, the referee may let that swimmer compete again in the next heat. If it happened in the last heat or in a final, the referee may order it to be swum again.
• Deliberate interference: reported for possible disciplinary action.

Each swimmer is given the same strip of water so that the race is decided by swimming alone. The rope, the bottom and the next lane are all things that could be used to go faster or to slow someone else, so each is put out of bounds. The re-swim exists because a disqualification punishes the offender and does nothing for the swimmer who was held up.