A sound made by tapping on the hull of a ship will be reflected from the sea bottom,

敲打船体所发了的声音会从海底传回来，

For this reason there is no risk to the customer in the practice,

因此，这种做法对储户毫无风险。

and it is only in the seas and rivers, and sometimes lakes, where mud and sit have been continuously deposited,

所以只有在泥沙不停淤积的海洋和江河里，有时在湖泊里，

the strangest of them being perhaps the hovercraft.

其中最新奇的要数气垫船了。

Such a loss of dignity and descent into childish behaviour on the part of the adults deeply shocks the adolescents,

这种有失身份和孩子气的作法使青春期的孩子大为震惊，

We could, at one time, repair ourselves----well enough, at least,

而我们人，在一定时间内是可以自行修复的，