I have noticed that oar handles are not varnished, and several kayaks and canoeists have noted that varnishing paddle shafts can cause blisters. If that is the case you may be better off either using nothing or an oil finish. My oldest tools had no finish that I could see, just plain wood. Sure they discolored with age but they were still the most comfortable tools I have (past tense because I lost most of them in a fire)