There are no standard services, but lots of ships do cross and many people bring their privately-owned boats, so it can be done.
Difficult to find a figure, since many boats are privately owned and could be intensively used or not at all.
Yes in many places in the world, stretches of river are privately owned.
There is no record of all the privately owned spaceships currently in existence. However, the first privately owned spacecraft, the SpaceX's Dragon was launched in 2010.
Yes, there are many privately owned islands in Hawaii. These islands can cost up in the millions.
4 million
About 250,000 aircraft not counting commercial, military or government owned. It is difficult to separate those rented or leased back.
Many Porter Paint stores are corporately owned however, there are privately owned dealers that also sell Porter Paint.
Many citizens were unwilling to give up their privately owned possessions
About 200 companies
Uncle Ben's is owned by Mars, Incorporated, which is a privately held company. So, in a technical sense, Uncle Ben's is owned by Mars.
Corporations are less risky than privately owned businesses or sole proprieties because they have many owners and each owner is only responsible for a share instead of the whole business being the responsibility of one person.