These data are high-resolution bathymetry (lake bottom elevation) in a gridded XYZ format, generated from hydrographic surveys of Geist Reservoir in April and May of 2016. Hydrographic data were collected using a multibeam echo-sounder (MBES) with integrated inertial navigation solution (INS) mounted on a marine survey vessel. Data were collected as the vessel traversed the lake along survey lines distributed throughout the area. Data collection software integrated and stored the depth data from the multibeam sonar and the horizontal and vertical position and attitude data of the vessel from the INS in real time. In the shallow areas, additional data were collected with an acoustic Doppler current profiler (ADCP) and a real-time kinematic global positioning system (GPS). Data processing required computer software to extract bathymetry data from the raw data files and to summarize and map the information.