Swimming is very popular in the world. Many people like swimming in summer, even in the other three seasons. Water makes people feel cool and swimming makes people keep fit. If you swim in a wrong place, it may not be safe. A lot of people died when they were enjoying themselves in water, and most of them were students. Now some people are not careful enough in swimming. They often think they can swim so well that nothing will happen to them in water. If you go swimming in summer, don't forget that a lot of good swimmers have died in water. They died not because they couldn't swim, but because of their carelessness . Don't get into water when you are alone. If there is a " No Swimming" sign, don't swim there. If you  remember these, swimming will be safe and enjoyable . Some swimmers died in water because they were  _  .
students children not strong too careless