Tā / niánqīng / shí / cháng / zài / jiāng / shàng / cāo / zhōu / duì / shuǐliú / de / biànhuà / shífēn / shúxī

他年轻时常在江上操舟，对水流的变化十分熟悉。

When he was young, he often steered boats on the river and became very familiar with changes in the current.