The hydrofoil usually consists of a winglike structure mounted on struts below the hull, or across the keels of a catamaran in a variety of boats (see illustration). As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull(s) develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides a corresponding increase in speed and fuel efficiency.

Wider adoption of hydrofoils is prevented by the increased complexity of building and maintaining them. Hydrofoils are generally prohibitively more expensive than conventional watercraft above the certain displacement, so most hydrofoil craft are relatively small, and are mainly used as high-speed passenger ferries, where the relatively high passenger fees can offset the high cost of the craft itself. However, the design is simple enough that there are many human-powered hydrofoil designs. Amateur experimentation and development of the concept is popular