下面这句话中“wade down”是固定短语吗？为什么要加个“down”？可以去掉吗？

Question

The men of our family waded down through our flooded meadows with boathooks, in the hope of being able to grapple a corner of the raft and pull it out of the current towards our bank.(我家的男人们手拿船篙蹚过被水淹没的草场，希望能够钩住筏子一角，将它拽出激流，拖回岸边。)——《新概念英语》

Answer 1

wade是动词， 跋涉，涉，蹚（水或淤泥等） 的意思，后面一般是加副词或介词，这里的down就是向下的意思，指出方向，表示他们向下蹚过被水淹没的草场。