already posted to r/minecraftsuggestions
For a better explaination, we know villages extend their pathways over water with little wooden bridges. So my suggestion is that if a village is close enough to an ocean biome that said bridge extends into the ocean then there will be a large ship there. The specific conditions you'd need to find one of these ships means that they're very rare and would be a worthwhile treasure.
The ship would be roughly the size of a typical large house in the village. Like a normal boat you can sail it around and even walk on it. You will find that the boat has several places to click to access a few different functions.
On the sides of the ship, chests are built into the hull and you can only access them there. The ship can hold 4 double chests worth of storage.
On the deck, you can right click on one of 8 slabs to sit down and become a passenger. Animals brought onto the ship will automatically sit on any of these slabs.
On the deck of the ship is also a sail that opens when the ship is in motion. Right click with a banner to customize it.
On the back of the ship is the captain's chair with a steering wheel at the front and a furnace behind.
Controlling You can turn the ship with the same controls as a normal boat but you need to right click the furnace with fuel to make the ship move forward. But when the ship starts moving, it will not stop until the fuel runs out so you'd have to be strategic about what fuel you use. Want to move the ship just a smidgen? Burn a wooden plank. Want to sail from one end of the ocean to the other? Drop a coal block. Want to troll your friend whos pulling into a tight dock? Sneak onto the ship and drop a lava bucket! They'll be confused and sailing in circles forever!
Sinking Enough collision will cause the ship to sink. It will not be destroyed and will not despawn. Infact, the ship is indestructable and can only be damaged enough to sink. It sinks at the rate of 2 block per minute.
You can dive to the bottom of the ocean and right click on the ship with wood planks to repair it but it would still be sunken. You'd have to create bubble columns beneath it to fill the hull with air so it floats back up.
Either that or bring a group of friends with fishing rods to team-reel the ship out of the water.