简答题 翻译：Many physical-fitness enthusiasts consider the English Channel to be the supreme test of a swimmers endurance.During the past 100years，the body of water separating England from France has been the scene of more than 1000attempted crossings.The high waves and freezing temperature of the water make it especially difficult.Matthew Webb was the first person to succeed.An experienced swimmer，the Englishman prepared for the history-making event by undertaking several long-distance swims，including a record-breaking swim of twenty-one miles in less than five hours.In 1879，Webb swam the Channel from Dover to Calais in twenty-one hours and forty-five minutes.Many swimmers have successfully accomplished the feat since then.To prevent cheating，a group called the Channel Swimming Association was created to supervise all attempted crossings.The association also provides an observer in a rowboat to ensure each swimmers safety.