If your house happens to have the ability to float, does that make it a boat? The Supreme Court recently considered this question, and came to the decision that a house is a house, regardless of its buoyancy.
For many years, people living on houseboats have argued that these homes are not "vessels," and should not be placed under the rule of maritime law. Up until now, however, the state of Florida persisted in treating houseboats as legal "vessels," which meant that houseboats fell under the jurisdiction of an entirely different set of laws than those in effect on land.
The houseboat owner in this legal case apparently owed some fees to the city marina where his houseboat was docked. Under maritime law, his "vessel" could be seized and held or destroyed, whereas under regular property laws his home would have had many more protections.
The central fact which swayed the Supreme Court justices in the homeowner's favor was the question of whether the two-story home (moveable only by towing) qualified as a "means of transportation." Justice Stephen Breyer even included a photo of the houseboat in his written opinion, in which he expressed the majority opinion that this house could not reasonably be treated as transportation simply because it floats.
Unfortunately, the Supreme Court ruling came too late to be helpful to the homeowner: the marina had already seized and destroyed the houseboat, which they were permitted to do under maritime law.
This case provides a vivid illustration of the fact that maritime law has standards and outcomes which may differ drastically from those which we're accustomed to on land.
Source: The Associated Press, "Floating home not covered under maritime law," Jesse J. Holland, Jan. 15, 2013