因为短语be interested in doing something,sit 和do 都是动词,所以要用ing形式
I am only interested in sitting in a boat and doing nothing at all.
翻译：
我感兴趣的是乘坐独木舟,什么事都不干.After having spent whole mornings on the river, I always go home with an empty bag.这个里面为什么用havingafter 是介词介词之后的动词都是用ing形式吗？恩呢