How many letters does the top answer for “a person who travels through the water by swimming” have?

The most common answer is bather (6 letters).

Crossword clue: a person who travels through the water by swimming

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

bather 6 letters wn-def

a person who travels through the water by swimming

swimmer 7 letters wn-def

a person who travels through the water by swimming