I have done some research this year in to the best value in a ~$200 fishfinder and the
Eagle FishMark 320 seems to be one of the better deals for inshore use. The Furuno units don't appear to work as well in shallow water (say, less than 4 feet) and the Garmin units are known for screen problems.
The Eagle Fishmark 320 (
http://www.eaglegps.com/Products/Sonar/fishmark320.htm ) is essentially the same as the Lowrance X87 (
http://www.lowrance.com/Marine/Products/X87.asp ), which is about $70 more.
You might find it a little cheaper, but Cabelas has it for $199.99 with a free screen cover. Search
http://www.cabelas.com Item ID-015619.