Wordnet 3.0
NOUN (1)
1. 
 a person who travels through the water by swimming; 
- Example: "he is not a good swimmer"[syn: swimmer, natator, bather]
WordNet (r) 3.0 (2006):
natator
    n 1: a person who travels through the water by swimming; "he is
         not a good swimmer" [syn: swimmer, natator, bather]