Abstract: An installation for extracting energy from a liquid in which swell occurs relative to a bottom. The installation includes a first and second container for placing at a determined horizontal first mutual distance at least partially under the surface of the liquid, each provided with a closed upper side directed toward the liquid surface, closed side walls and an open underside directed toward the bottom for enclosing a gas under the liquid surface. The gas is bounded to the underside of the container by a quantity of liquid entering via this underside, which quantity of liquid varies as a result of the swell. A transport conduit is provided for transporting gas from the first to the second container and vice versa. A generator responding to the variation in the quantity of liquid in at least one of the containers for generating energy from this variation is also provided.