如鱼得水的英文：
[Literal Meaning]
like/fish/get/water
to feel just like fish in water

[解释]
好像鱼得到水一样。也比喻得到跟自己十分投合的人或对自己很合适的环境。

[Explanation]
to be at great ease

[例子]
将军有了这个谋士之后，如鱼得水，很快就打了几个胜仗。

[Example]
After the general had the advisor, he was at great ease and won in a few battles soon.

[英文等价词]
as a duck takes to water
in one's element

Casting, rehearsing, sketching stage sets—he even took the lead in one of his own dramas—he was in his creative element.
他亲自选派角色，参加排演，画布景，甚至主演自己写的一个剧本，他对这些都很内行，如鱼得水。