a stagnant pool; like a pool of standing water ❍ 那个不平凡的举动，使～的清朝政局，激起了一阵波浪。That was a major action agitating the stagnant pool of Qing Dynasty politics.
一潭死水yī tán sǐ shuǐ
潭：深水池。一池子的死水。比喻停滞不前的、死气沉沉的局面。a pool of stagnant water, stagnant or lifeless condition