A Deadly Current

It is a pity that every summer a few people drown at the beach. In some cases, these people were good swimmers. So how did it happen? Riptide!
  Riptide is a strong underwater current. It moves quickly away from shore and out to sea. It appears suddenly and pulls its victim under and far off shore. Therefore, people should make it a rule never to swim too far out from the beach.
  If you find yourself in a riptide, don't panic. And by no means should you try to go against the tide and swim back to shore. You'll tire yourself out and probably drown. Instead, swim parallel to the beach. A riptide is very narrow. So just a few strokes in the right direction and you'll be out of danger.

  很遗憾, 每年夏天总有一些人在海边溺毙, 而这些溺水的人中有些是很会游泳的。那么这究竟是怎么发生的呢?是激潮在作祟!
  激潮是海面下一种强大的暗流, 从海岸迅速地流向大海。它出现的时候毫无预警, 会将受害者拉下水面并拖离岸边。因此, 人们应该养成不要游得离海滩边太远的习惯。
  假如你发现自己被卷入激潮时, 别惊慌。而且千万别试图逆着潮水往岸上游, 那会使你筋疲力竭而可能遭到灭顶。你游的方向应该和海滩保持平行。激潮的范围很窄, 所以只要朝正确方向游几下, 那么你就能脱离险境了。