Abstract: Apparatus and method for inducing directed water movements for treatment of large water bodies subject to surface freezing, stagnation, bottom oxygen deficiency, or other non-uniform conditions. The apparatus consists of an open axial-flow impeller, driven by a motor, supported from below by a streamlined structure, totally submerged in a water body to avoid proximity to the surface, and resting on the bottom of the water body. The rotation of the impeller produces a water movement directed as aimed. A method is disclosed whereby dissolved oxygen is renewed in ice-bound water bodies by raising warm bottom water to melt surface ice, thereby creating an area of open water exposed to direct atmospheric oxygen diffusion and photosynthesis, and simultaneously circulating oxygen enriched water to remote parts of the water body.