The members of a relay team and their order of competing must be nominated before the race. Any relay team member may compete in a race only once. The composition of a relay team may be changed between the heats and finals of an event, provided that it is made up from the list of swimmers properly entered by a Member for that event. Failure to swim in the order listed will result in disqualification. Substitutions may be made only in the case of a documented medical emergency.