So AFAIK,

• You can use ships to travel into or through a claim
• Boats sailed into a claim may provide a place to fight from
• Boats sailed into a claim may provide a means over a wall or on top of a base
• Tow ships (attaching a ship to another ship) is allowed to steal a ship or a ship being built
• Use boats to move cannons, mortors, TNT dispensers into a claim during a fight

What you can not do:

• Do not power a redstone device with a ship
• Do not intentionally ‘detach’ parts of your ship to leave behind
• Do not use ships to move existing claim blocks (like attaching to buildings, walls, etc. or using sticky pistons)
• Do not use ships to grief claimed land (dispense lava, etc)

Please do not intentionally /release them adjacent to another structure such that they attach themselves. This allows the owner or you (hopefully) to sail the ship away without hassle. Also please make reasonable effort to remove and destroy these ugly things so that admins do not need to.