The workers had to go far below the softbottom of the river. They had to reach rock and remove some of it in order to make a good base for towers.
工人们必须深入软河床下面，必须接触到地底的岩石并挖开它们，以便为塔构筑坚实的基底。
3
We explored the streams, quietly, where the turtles slid off the sunny logs and dug their way into the softbottom; and we lay on the town wharf and fed worms to the tame bass.