During the Three Kingdoms (sān guó 三国) , Liu Bei (liú bèi 刘备) went to Longzhong (lóng zhōng 隆中) three times to ask Zhuge Liang (zhū gě liàng 诸葛亮) to assist him. Finally, Zhuge Liang helped Liu Bei deal with military and politics affairs, and was significantly trusted by Liu Bei. Their respect for each other became more deeper. Liu Bei said to his ministers: "Having Kong Ming (kǒng míng 孔明) help me, I feel just like a fish which has been put back in the water."This idiom is used to signify finding a boon companion (愉快的伙伴) or an ideal situation.

三国时期，群雄争霸。刘备为实现统一大业，特意三次拜访隐居在隆中的诸葛亮，请他出山。最终孔明同意辅佐刘备，刘备对孔明也十分信任。刘备对他的大臣说：“我刘备有了孔明，就好像鱼儿得到了水一样。” 此成语用来比喻得到和自己志趣相投的人或对自己很合适的环境。

 如鱼得水 ( rú yú dé shuǐ )
【翻译】 To Feel Just like a Fish in Water
【释义】 好像鱼得到水一样。比喻得到跟自己十分投合的人或对自己很合适的环境。
【例句】 小张能力强，做班长如鱼得水，把班级管理得有声有色。
【近义词】 如虎添翼、情投意合
【反义词】 寸步难行、举步维艰