语法总结
had hardly ... when ...
原文用 had hardly had time to realize... when... 写出几乎来不及反应，事故就发生了。
相似句：
- He had hardly sat down when the phone rang.
- We had hardly left when it started to rain.
过去完成时交代先前撞击
the speedboat had struck a buoy 说明在人物发现新危险前，撞浮标已发生。
相似句：
- The train had already left when we arrived.
- She had locked the door before going upstairs.
because 引导原因
they swam on... because they knew... 直接把动作和判断连起来。
相似句：
- He ran because he heard a shout.
- She stayed calm because she knew help was coming.