赖氏中级 死亡暗流

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.