Hydrofoil

What it means

A hydrofoil is a wing below the hull. As the boat gathers speed the wing generates lift, the hull rises clear of the surface, and the only parts still in the water are the foils and their struts. The boat is flying, in water rather than air.

Why it suits electric boats

Drag is what empties a battery, and most of a boat's drag comes from pushing water aside. Lift the hull out and that resistance largely disappears: a foiling boat can travel at speed on a fraction of the power a displacement hull needs, which turns a modest battery into a useful range. It is one of the few ways to have both speed and distance on stored electricity.

Why it matters

The gains come with conditions. Foils need a minimum speed to lift, add draught when lowered, demand a control system to hold the boat steady, and are unforgiving of debris. Foiling boats also tend to be the most software-dependent vessels in the catalogue, which is a different kind of ownership.