swim-off

noun2

1. •
   A special swimming race in which the winner gets to compete in the next level of trials (typically the finals), where the competitors have not qualified for the next level by the usual elimination races.

   • If the disqualifications leave a vacancy for the full complement of finalists, swim-offs shall be continued among the disqualified swimmers until a full complement of finalists is assured. — 1973
2. •
   The start of a period, in which the two teams try to reach the ball placed in the centre of the pool.