A swimmer is a person who swims, especially for sport or pleasure, or a person who is swimming. You don't have to worry about me. I'm a good swimmer. a someone who swims well, often as a competitor good/strong swimmer
a person who travels through the water by swimming; "he is not a good swimmer" a trained athlete who participates in swimming meets; "he was an Olympic swimmer
a trained athlete who participates in swimming meets; "he was an Olympic swimmer