Have you ever seen a windmill on land spinning around and making electricity? Well, imagine that windmill is put onto a ship! This is called a windmill ship.
The windmill on the ship has big blades that catch the wind just like a regular windmill. When the wind blows, the blades start spinning and make power that is used to move the ship. It's like having a sail that you don't have to adjust or take down.
The windmill ship is also really good for the environment because it doesn't use any fuel like oil or gas. This means it doesn't make any pollution or harm the air we breathe.
The windmill ship might be slow compared to other ships but it's very efficient and it doesn't need any fuel and that's really cool, right?