A fish finder is an electronic device used by anglers to locate fish underwater. It works by sending out sound waves, which bounce off objects like fish and the seabed. The device then interprets these echoes and displays the information on a screen, showing the depth and location of fish. Fish finders come in various types, including portable models and those built into boats. Many modern fish finders also feature GPS technology, allowing users to mark fishing spots and navigate more easily. They are popular tools for both recreational and professional fishermen, enhancing the fishing experience.