Shipwreck

When a ship has no living people on board (or in cabins and holds) and has been unvisited by people for 200 days, it gets a 2% daily chance of being destroyed and turning into a shipwreck.

If a boat weighs 7000 grams or less, it will become a small shipwreck. If it's heavier than this, it will become a large shipwreck. The shipwreck will appear in a coastal location and it will have no lock, so anybody can enter and see, and optionally loot, what ever remains inside. Notes will always survive a shipwreck, but most resources and objects inside will be destroyed. Shipwrecks are similar to cages in that people inside will be visible from the outside but you naturally can't undock them or take them down a road.

A large shipwreck takes 5 days to disassemble with an axe and sledgehammer, giving 7000 grams of wood.

A small shipwreck takes 2 days to disassemble with an axe and gives 1800 wood. (Even if it was originally a kayak or a reed boat and didn't take wood to build.)