The greyscale
fish finder I mostly use is a Northstar 443s and it has provided excellent
service for bottom condition evaluation for many years. It was the cheapest available at the time I bought it and has a
navigation mode which displays large numerals easily seen from the
cockpit down the
companionway. Unfortunately I think this model has now gone out of production.
The previous one I used was a Hummingbird greyscale and it also gave excellent
service. I think that just about any
fish finder is going to give better service than just a
depth indicator. One of the features I really like about them is you can see whether the
depth is shoaling or increasing at a glance from the trending of the bottom indication.