To reduce the energy required to propel the boat, windmill ships are often equipped with low-friction hull designs, such as multihulls, or they are hydrofoils.
In this case, the turbines only provide supplemental force to conventional sails or other propulsion systems.
For example, high horizontal axis windmills are proven to make the ship less stable.
[4] Also, the wind mill needs to be highly durable as marine environments tend to degrade windmills more quickly than what is common on land.
[5][6] Few windmill ships have been built to date; these include:[7] The film Waterworld starring Kevin Costner featured a trimaran powered by a vertical-axis Darrieus wind turbine.