Fish can swim well with their fins in water. 鱼因为有鳍能在水里畅游。

　　Also, fish cannot move without fins. 相反的，没有鱼鳍，鱼就不能游了。

　　Do you know that different fish have different shapes of fins? 你知道鱼的种类不同，鳍的形状也不一样吗？

　　Some fish have round fins, these round-shaped fins are strong, but the fish can swim slowly. 有些鱼鳍是圆状的，这些圆状鳍很强壮，但这种鱼游得也很慢。

　　Some fish have a crescent-shaped fin, fish with fins shaped like this can swim fast. 有些鱼鳍是新月状的，有这种鱼鳍的鱼游得很快。

　　Fins are very important to fish. 鱼鳍对鱼非常重要。