"作尾桨手" can be translated as "serve as the stern oarsperson" or "act as the stern paddler" in English, depending on the context (e.g., rowing, canoeing, etc.).
If referring to a rowing context (like in a rowing boat), "stern oarsperson" would be appropriate.
If referring to a canoeing or kayaking context, "stern paddler" might be more fitting.
For a more general or colloquial expression, you could also say "be the one at the stern (rowing/paddling)".