The Great Lakes Mapping Act directs the National Oceanic and Atmospheric Administration to create high-resolution maps of the lakebeds of all five Great Lakes by December 31, 2029. The mapping effort will collect detailed bathymetric data, develop methods to process this information, and create a searchable system to catalog all lakebed data collected during the project. The bill authorizes 200 million dollars in federal funding through fiscal year 2030 and requires the NOAA Administrator to work with state governments, coastal observing systems, and other relevant agencies to complete the work. Completed portions of the maps will be made available to the public as they are finished, with the full map and all related data released within 180 days after the project is complete. This legislation affects Great Lakes states and the public by providing detailed underwater mapping that can support navigation, environmental protection, and scientific research in the region.