In Britain nowadays,canals are used mainly for pleasure by people travelling in long, narrow boats.
翻译:
如今在英国，运河主要被乘坐狭长船只的人们用于休闲娱乐。
知识点解析:
现在分词作后置定语。travelling in long, narrow boats 修饰前面的 people，表示主动关系（人们“乘坐”船）。