A depth finder is a device used to measure the distance from the water's surface to the bottom of a body of water. It helps boaters, fishermen, and divers understand underwater terrain and locate fish. Depth finders use sonar technology, sending sound waves that bounce off the seabed and return to the device, providing accurate depth readings. These devices come in various forms, including handheld units and those integrated into boats. Many modern depth finders also feature additional capabilities, such as mapping underwater structures and displaying water temperature. They are essential tools for safe navigation and effective fishing in lakes, rivers, and oceans.