The Humminbird 678c HD XD is a unit that offers only fish finding features, and does not support any navigational features. However, it's an extreme depth fish finder (that's what XD stands for), with a depth capability of 3,000 ft. The head unit of the 678c HD XD is similar to the other fish finders from the 600 series, featuring a full color, 5-inch diagonal screen, 480H x … [Read more...] about Hummingbird Fish Finder 678c HD XD Review