Comme un poisson dans l'eau

At her first day working in a bustling Paris café, Léa didn’t miss a beat; taking multiple orders, joking with regulars, and balancing three plates like a pro. While everyone else was still figuring out the espresso machine, she was gliding from table to table comme un poisson dans l’eau, as if she’d been doing it her whole life.
The French expression comme un poisson dans l’eau literally means “like a fish in water”- and honestly, it’s exactly as breezy as it sounds.  It’s used for someone who is totally in their element; relaxed, confident, maybe even thriving a little too much.

In English, you’d say: “like a duck to water” . Same energy: effortless, natural, and maybe just a tiny bit enviable.

Origin

Unlike many idioms that feel arbitrary, this one makes immediate sense.  Picture a fish, in water, living its best life. No awkward flopping, no existential crisis, just smooth swimming.  That image has been floating around French since the 16th century, and it stuck because, well… it’s spot-on. A fish doesn’t try to be comfortable in water - it just is.  When French speakers use the phrase, they’re not just saying someone is comfortable, but that they’re in their natural element, almost as if they wouldn’t function as well anywhere else.  

There’s also a subtle cultural nuance: the phrase is often used in contexts involving social ease or intellectual comfort. Someone might be comme un poisson dans l’eau at a dinner party, in a classroom, or even while speaking a foreign language. It’s not just physical comfort; it’s fluency, confidence, and belonging, all rolled into one.

Examples

Elle parle en public comme un poisson dans l’eau.
She’s completely at ease speaking in public.

Dès son arrivée, il était comme un poisson dans l’eau.
He fit right in from day one.