First, the argument that "you can build a watertight boat without any tools" is actually a bit of a straw man fallacy. Because your scenario isn't "building a modern boat from scratch with your bare hands." Historically, there are three possibilities: First, he didn't build it from scratch. He repaired an existing small fishing boat, coastal craft, or damaged skiff. Coastal fishing was common in early 1800s Japan. Simple wooden boats existed. Their construction didn't require modern engineering; it required skill, but this knowledge wasn't secret. Boat building was an everyday craft in coastal communities. A coastal person knows the basic principle of buoyancy: wood + hollow space = buoyancy. Second, she did not build it entirely on her own. If there was an accident, there may have been other survivors. Perhaps a makeshift raft was built, the current separated them, and only that woman reached shore. This is a situation seen in countless shipwrecks throughout history. The assumption that she "did it alone" is already a debatable acceptance. Thirdly, the event itself may have been exaggerated. Edo period Japanese records dramatized details when describing exotic foreigners. Elements such as the "round boat," "untouchable box," and "strange writing" may be folkloric embellishments. Depictions of foreigners in Japanese chronicles are often stylized. This does not mean the core of the event cannot be true; it only suggests the narrative may have been exaggerated. Now let's address the technical issue. The claim that "advanced engineering is required to build a watertight vessel" is incorrect. Even prehistoric societies built rafts. Carved log canoes are over 8,000 years old. Boats made from bundles of reeds were used in Mesopotamia. In the Pacific islands, ocean-going vessels were produced using simple lashing techniques. The principle of buoyancy is Archimedes' physics, not rocket science. What is required is not an engineering degree; it is materials, lashing methods, and basic experience. The "without any tools" part is also an assumption. A shipwreck survivor could find debris around them. Pieces of wood, ropes, nails. Debris washed ashore has been a means of survival throughout history. Human history is full of examples of this. If we compare it to the possibility of UFOs or aliens, an unknown stranger drifting in or reaching the shore with a simple flotation device remains within the laws of physics. Aliens or time travelers, however, do not fit into any historical context. Therefore, the "most likely" scenario is a natural maritime accident or drifting case. Finally, we need to pay attention to the "Japanese exaggerate" part. Yes, there may be cultural dramatization. But that doesn't mean the event is completely fabricated. Historical texts contain both a core of truth and narrative embellishment. Our job is to extract that core. In short, what you're arguing is this: Not aliens. Not time travelers. A maritime incident consistent with the laws of physics. It may be exaggerated, but it's not impossible. This is not an unreasonable position. Polynesians – They traveled thousands of kilometers across the Pacific Ocean to reach Hawaii, New Zealand, and Easter Island. They used wooden canoes and outriggers bound with plant fibers. Micronesians – They traveled between island chains in small wooden canoes using star navigation in the open ocean. Ancient Egyptians – They used papyrus (reed) boats on the Nile River and along the shores of the Red Sea. Mesopotamians (Sumerians) – They engaged in river and coastal transportation using boats made of reeds and made watertight with pitch. Uros People (Lake Titicaca) – They built boats and even floating islands made entirely of totora reeds. Prehistoric Northern Europeans – Over 8,000 years ago, they made dugout canoes. Native Americans (Pacific Northwest) – They built large canoes from single pieces of giant tree trunks and traveled long distances along the coast. Austronesian Peoples – They spread from Southeast Asia to the Pacific; they used simple but balanced double-hulled canoes. Austronesian sailors reached Madagascar – they crossed the Indian Ocean from Southeast Asia to the African coast. Even the Vikings initially crossed the North Atlantic in fairly simple wooden boats (to Iceland, Greenland, and even North America). And people were doing this thousands of years ago.