I'm looking for a fish finder. Prefer to keep cost under $500. Will be fishing local, small lakes and ponds pretty much exclusively. Therefore, I don't care about how it does beyond about 25 foot depth. I don't think I need GPS, maps, or any connectivity. I care very much about how it does in 5 foot depth. I'd prefer something that is pretty simple to use (I don't have time nor desire to spend hours learning how to interpret or fine tune). Would use on small (15 foot) pontoon boat or possibly on kayak most of the time. Any suggestions?