They can be used for open water fishing or ice fishing, but work best when used with small boats.
They typically consist of a nylon carry case that holds all the components of the portable kit: A small fish finder unit (3 to 7 inch screen), a plastic mounting base, portable transducer, and a small rechargeable 12V battery.
Humminbird HELIX 7 CHIRP GPS G3N All-Season
