"I know how to swim easily."
Translation:Je sais nager facilement.
"I know how to swim easily," as opposed to swimming in a difficult manner? I'm not sure what this sentence actually means.
In English we just have the verb "to know". In French there are two verbs for knowledge and they are distinct and not interchangeable.
to know how to do something. Il sait jouer du violon. He knows how to play the violin. Elle sait cuisiner. She knows how to cook.
to "know" with a subordinate clause. Je sais où elle est. I know where she is.
to know a person personally. Je connais Samuel. I know Samuel.
to be familiar with a person, place, or thing. Angela Merkel? Oui, je la connais. Angela Merkel? Yes, I know (am familiar with) her. Je connais Bordeaux. I know (am familiar with) Bordeaux.
In the passé composé connaître means to meet for the first time. J'ai connu Mark à New York.