GIS is short for geographic information system. From Wikipedia: “In a general sense, the term describes any information system that integrates, stores, edits, analyzes, shares, and displays geographic information. GIS applications are tools that allow users to create interactive queries (user-created searches), analyze spatial information, edit data in maps, and present the results of all these operations.[2][3] Geographic information science is the science underlying geographic concepts, applications, and systems.”
Douglas County recently upgraded their GIS offering in a big way and have made it easy to find information about real estate and the layer with leaf-off aerials from 2016 also will give you a very good feel for water depth and the bottom of the lake. Check it out. It is a wonderful tool. Below is an example in a screenshot of a portion of an area of Three Havens.