Ducks are very comfortable in water, so when we say that someone 'took to it like a duck to water', it means that we recognise how comfortable they are with something, or how suited to the task or experience they are. You can use this in either Social or Professional contexts, but it is slightly informal.

1. Carlos is starting his English lessons tomorrow. Knowing how smart he is, I think that he'll take to it like a duck to water.
2. Anne has taken to the piano like a duck to water. What a natural musician she is!

1. At first I really wasn't sure how Tom would get on in his new job, but I'm pleased to say that he took to it like a duck to water!