Provided are, among other things, systems, methods and techniques for generating energy. According to one representative embodiment, a main housing includes an air chamber having an open bottom, and a paddlewheel is attached to the main housing so that the paddlewheel is free to rotate and thereby generate kinetic energy. An anchor is attached to the main housing, and an electrical generator which converts the kinetic energy of the paddlewheel into electrical energy is coupled to the paddlewheel. An upper portion of the paddlewheel is enclosed by the air chamber. When the main housing is submerged underwater and maintained in a level orientation, air within the air chamber remains trapped within the air chamber, thereby reducing resistance to rotation of the paddlewheel.