An efoil is a board with a battery, a motor and a hydrofoil wing underneath. Squeeze the throttle and, once you are up to speed, the board rises clear of the water on the foil and you glide along almost silently, with no waves or wind needed. It feels like flying, because more or less you are.
It looks impossible and is more learnable than you would think. You start lying down, then kneeling, then standing, with an instructor managing the throttle and the learning curve. Most people are foiling, at least in bursts, within a session or two.
The instructors on adventuro run efoil sessions on calm water with the board and safety gear provided. Expect a few splashy starts before you unlock that silent, gliding magic.