After it had passed, they swam on as quickly as they could because they knew that the boat would soon return. They had just had enough time to swim out of danger when the boat again completed a circle. On this occasion, however, it had slowed down considerably. The petrol had nearly all been used up Before long, the noise dropped completely and the boat began to drift gently across the water.

　　句子讲解：

　　8、After it had passed, they swam on as quickly as they could because they knew that the boat would soon return.

　　快艇过去后，他们以最快的速度向前游去，因为他们知道快艇马上就要转回来。

　　语言点 as they could为比较状语从句

　　as quickly as 以最快的速度

　　as soon as possible 和as quickly as possible有什么区别?

　　as soon as possible:尽早 (指时间上早一点)

　　as quickly as possible:能多快就多快 (指行动的迅速)

　　9、They had just had enough time to swim out of danger when the boat again completed acircle.

　　当快艇又转完一圈时，他们刚刚来得及游出危险区。

　　语言点 have enough time to do sth.有足够的时间去做某事

　　just是个可以和各种完成时连用的时间副词，它与when连用时常用于过去完成时：

　　Jim had just left when you rang.

　　你打电话时吉姆刚走。

　　The patient had just died when the doctor arrived.

　　医生来时病人刚死。

　　10、On this occasion, however, it had slowed down considerably.

　　然而,这一次快艇的速度慢多了。

　　语言点 slow down减速

　　occasion：

　　n.场合; 机会，时机; 理由; 需要;

　　vt.惹起，引起;

　　I'll dress for the occasion.

　　我会为这个场合慎重打扮的.

　　considerably:

　　adv.相当，非常，颇;

　　[例句]Considerably more than what they're paying.

　　远比他们现在所得的要高很多。

　　11、The petrol had nearly all been used up.

　　汽油就要被消耗光了。

　　nearly:

　　adv.几乎，差不多; 险乎;

　　[例句]A bridge nearly killed us.

　　一座桥差点害死我们。

　　12、Before long, the noise dropped completely and the boat began to drift gently across the water..

　　没过多久，噪音就完全消失了，船开始轻轻地漂流

　　drift：

　　vi.漂泊; 流动; 随意移动; 浮现;

　　vt.漂流; 堆积成堆;

　　n.漂移，偏移; 趋势，动向; 大意; 放任自流;

　　[例句]To compensate for stellar drift.

　　以补偿星体的漂移.

　　扩展：

　　几个英语单词的意思和用法：before long 、 long before 、long after、soon after

　　before long是不久以后,等于soon;long before是很早以前,等于long long ago

　　long after很久以后 soon after 不久之后,稍后,after是连词,后面跟一个句子.

　　before long 是“很快,不久”的意思,可以用于各种时态.是词组表示时间,单独用.

　　例如:

　　1).I'll see the film before long 我不久就要看这部电影.

　　enough与fairly的区别

　　enough表示“足够”，用在形容词或副词之后，有“为了某种目的”的含义;

　　fairly表示“相当”，通常修饰表示肯定意义的词：

　　I'm old enough to know what I'm doing.

　　我已经大了，知道自己在干什么。

　　He is fairly quick, but not quick enough to take part in the race.

　　他跑得相当快，但要参加比赛还不够快。