水を得た魚

みずをえたうお

expression, noun

•

someone who is in their element, fish that has found water(idiom )

水	water
得	gain, get, find, earn, acquire, can, may, able to, profit, advantage, benefit
魚	fish

はたけ

しごと

かれ

みずえうお

He's in his element when working on the farm

かのじょ

みずえうお

She is in her element when it comes to tennis