GSD 28 Advanced Sonar ModuleSee whats down there. Catch whats down there. Take sport fishing to extreme depths with a high-powered sonar module with the features that are needed to improve the chances of success.FeaturesEngineered for offshore sport fishingSee sonar faster with Garmin RapidReturn technologyCrisp and clear fish targets with Xchirp technologyExcellent target separation with xCHIRP technologyGreatly reduce wave and swell from bottom returns with heave compensationGarmin RapidReturn