An oarsman is someone who rows a boat, especially in a race. The picture in most people’s heads is a person in a long, thin racing boat, pulling in time with a team. The word is built as a male job-word, like policeman, and older sports writing used it that way. Though actually many people now just say rower for men and women, because it is simpler and does not pick a gender. You will still hear oarsman in club names, old reports, and some race talk. The plural is oarsmen. It does not mean a person who makes oars, and it is not used for someone steering with a single paddle in a canoe in the tourist sense — it belongs to rowing.