Personal property is any type of tangible property that is designed or generally allowed to be moved from one place to another. Large size is not relevant to this analysis. A ship can be many times larger than a shack, but a ship is still personal property while a shack is real property.
Personal property that is permanently or substantially fixed to land becomes a fixture and is then considered to be part of real property.
Establishing clear title to personal property can be difficult given its transient nature. Most large pieces of personal property, such as ships, aircraft and automobiles, must carry on them some indication of where their title is registered. This is why ships have their port painted on the back, automobiles carry license plates, and aircraft carry an identification number keyed to their state of registration. Generally, the courts of the jurisdiction of registration have final say over legal disputes regarding such property. For other personal property, jurisdiction lies in the territory where the personal property is actually present.