GSD 28 Garmin Sonar ModuleGSD 28 Garmin Sonar Module Garmin GSD 28 Sonar Modules are a high powered, black box sonar designed for serious offshore sport fishing, offering extreme depth capabilities and enhanced target separation through advanced CHIRP technology. It provides fast, detailed underwater imaging to compatible Garmin chart plotters. Garmin GSD 28 Sonar Module Key Features Extreme Depth Performance: Capable of reaching maximum depths of up to 10,000 feet (3,048