having spent the night in the water 是現(xiàn)在分詞短語用作狀語.根據(jù)上下文,既可以理解為時(shí)間狀語,也可以理解為伴隨方式狀語；前者說明她向海岸游去的時(shí)間,后者補(bǔ)充說明向海岸游去的時(shí)候伴隨著的行為方式”.
可以作如下改寫：
1. 用 and 改寫為并列句：
She had spent the night in the water and swam to the shore. 她在海水里已經(jīng)度過了一個(gè)夜晚,接下來向海岸游去.
2. 用 when（= at that time）改寫,相當(dāng)于并列句（從句不可以提到主句前）：
She swam to the shore having,when she had spent the night in the water. 她向海岸游去,此時(shí)她在海水里已經(jīng)度過了一個(gè)夜晚.
3.改寫為時(shí)間狀語從句：
After/when she had spent the night in the water,she swam to the shore. 她在海水里已經(jīng)度過了一個(gè)夜晚以后向海岸游去.