to feel just like a fish in water如鱼得水
In the late Eastern Han Dynasty, the country was in confusion.
In order to reunite the country, Liu Bei paid a visit to Zhu Geliang who had hidden himself in the countryside.
He went there twice but didn't see Zhu Geliang. Then the third time he finally met him.
Liu Bei explained why he came and explained his noble ambition to Zhu Geliang.Zhu Geliang also proposed some very good strategies.
After listening, Liu Bei was so happy, he appointed Zhu Geliang as his military advisor.He said: "Zhu Geliang to me is as water is to fish."
With the assistance of Zhu Geliang, Liu Bei's power expanded rapidly, and finally he realized his goal.
Nowadays, this phrase is often used to describe the person who stays in the environment which suits him/her perfectly, or someone who is very adept at using the suitable or right methods.
“如鱼得水”用英文可以表达为“feel just like a fish in water”，我们来看一个例句：
I've wanted to study at Beijing University my whole life. I also love the culture and the weather in Beijing. I feel just like a fish in water.