33. 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.