the problem is freeboard https://en.wikipedia.org/wiki/Freeboard_(nautical) https://en.wikipedia.org/wiki/Freeboard_(nautical) , i.e. the height of the "wall" o

the problem is freeboard https://en.wikipedia.org/wiki/Freeboard_(nautical) https://en.wikipedia.org/wiki/Freeboard_(nautical) , i.e. the height of the "wall" of the sides of a ship to keep the splashy water out. Oars need to be relatively close to the surface of the water, and where there are oarlocks water can get into the ship. Open seas are heavy seas, meaning the waves are very very high; six foot seas are nothing in the ocean, but a bitch to bob around in. And, in heavy seas you need deep draft--the "height" of the boat under water--for stability. Also, the "powerplant" and "fuel" for oars takes up too much space limiting the freight capacity of a ship. This is basically why rowing technology was abandoned for sailing around the world or across oceans. Paddle steamers were used somewhat, but the paddles just don't have the purchase against the surrounding water to move a heavy deep draft ship.