Summary: Most of the reviews for this are about the unit with side imaging. This model does not have side imaging, it is very misleading. Be careful what you buy. The 858c is good at what it does don't confuse with the si model.
Summary: I'm completely disappointed in the 858C. I've been trying to get it to work for over a month now, but it won't read depths deeper than 250-260 feet, even though this thing is supposed to work up to 1500 feet deep. Many calls to the support section at Humminbird have not resolved the problem. Tweaking settings have not resulted in any appreciable improvement. They sent me a new transducer that I will try this weekend.