This data is a large suite of coincident surface water observations for many different physical, chemical, and biological properties of the water in a reservoir in Southwest Ohio (Harsha Lake) at the time a flyover occurred to take hyperspectral images of the lake’s surface. 44 sites were visited across the reservoir within 2 hours. The data could be useful to others with interest in remote sensing of water quality or studying spatial patterns of water quality at one particular point in time. This dataset is associated with the following publication: Beck, R., M. Xu, S. Zhan, R. Johansen, E. Emery, M. Reif, C. Nietch, D. Macke, R. Stumpf, and M. Martin. Comparison of Satellite Reflectance Algorithms for Estimating Turbidity and Cyanobacterial Concentrations in Productive Freshwaters Using Hyperspectral Aircraft Imagery and Dense Coincident Surface Observations. JOURNAL OF GREAT LAKES RESEARCH. International Association for Great Lakes Research, Ann Arbor, MI, USA, 45(3): 413-433, (2019).