When it comes to the term "solo oarsman," there are several synonyms that can be used. For starters, you could use the phrase "lone rower." Another option is "single sculler," which is often used in reference to competitive rowing. Additionally, "solo rower" and "solo paddler" could also be used to describe someone rowing or paddling on their own. Whether you're writing about a professional rower or someone who enjoys taking their boat out on the water alone, there are plenty of options when it comes to finding synonyms for the term "solo oarsman".