A system for reducing an evaporation and energy transfer rate between a body of fluid and an environment is provided. The system comprises a plurality of buoyant bodies, where each of the plurality of buoyant bodies has a shape that is defined by a plurality of faces and edges, and where each edge is formed by two intersecting faces. The bodies are disposed or partially submerged in the fluid so that at least a portion of a first face of a first body contacts at least a portion of a first face of a second body to form a substantially gapless barrier between the surface of the fluid and the environment.