The Humminbird 561 DI is one of the cheapest models with Down Imaging. If you’re looking for a Humminbird unit strictly for finding fish, this might be it. Although it features only a black and white screen, 12 LvL Greyscale, it’s quite wide, 5-inch in diagonal, 320 x 320 pixel resolution. Evidently, it allows you to view both DI and classic sonar imaging in split screen.
It has Dual Beam Plus sonar, just as the Humminbird 561 simple, but the sonar capabilities are slightly different. It can operate at 200 kHz / 28° or 455 kHz / 16° in SwitchFire mode, or at 455 kHz / 75° and respectively 800 kHz / 45° in Down Imaging mode. This unit is capable of readings for depth up to 600 feet, while the Down Imaging features is reliable up to 300 feet.
Does not have any chartplotting capabilities, no waypoint memory, it’s not upgradable with an SD card. You actually get the basic fish finding options, plus Down Imaging, and that’s about it. However, its not a pricey unit.