A hydrofoil is a wing-like structure that is attached to the hull of a boat or ship and extends below the waterline. The purpose of a hydrofoil is to create lift, which in turn reduces drag and makes the boat or ship more efficient in terms of speed and fuel consumption. Hydrofoils are most commonly used on racing boats and other high-performance vessels, but they are also used on some commercial ships.
The first hydrofoils were developed in the late 19th century, but they did not become widely used until the 1950s. Since then, hydrofoils have been continually improving in terms of design and performance. Today, there are many different types of hydrofoils available, each with its own advantages and disadvantages.