If you're selecting a fishfinder for freshwater fishing, think about the water depth and type of craft you usually use. Unless you are fishing in truly deep water, like the Great Lakes, you can often get great results from some of the more inexpensive models. If you're in the marketplace for the first fish finder you might want to begin with a less complicated model and trade up to the more advanced models while you gain knowledge about finding fish easily.
Not all fish finders work well in all types of fishing. If you love to fish in freshwater then you need to locate a fishfinder that will work best for freshwater fishing.
In general single frequency fish finders are adequate for freshwater fishing. Single frequency fish finders work nicely in many lakes, rivers and in shallow coastal fishing and they're generally less expensive. Single frequency fish finders tight on depth penetration than dual frequency models, but for freshwater that's generally acceptable. Most freshwater fishing is not in deep water so being able to see to depths of 1000 feet or even more isn't needed. The single frequency fish finders will often have a larger cone angle that will allow you to visit a broader area in a more shallow depth.
If you happen to fish within the Great Lakes or any other very deep lakes or rivers then a dual frequency fishfinder assists you better. The dual frequency settings allows you greater visibility at deeper depth and overall deeper depth penetration.
Another facet of freshwater fishing to consider when choosing a fishfinder is exactly what type of craft you use for fishing. Many people use kayaks, float tubes, canoes or small boats when fishing in freshwater. If you use one of these simple smaller crafts you should think about a portable fishfinder. Both Eagle and Humminbird make portable fish finders which are both affordable and an excellent option for shallow freshwater.
For very shallow water, two to ten feet, one of the best choices is the Humminbird Fishin Buddy line. These fishfinders are portable and possess side viewing capability which allows you to see fish off to along side it of your boat. Plus you can adjust the shaft on these models to determine at different depths. There are several different types within this line and they're all inexpensive. If you want fixed mounted fish finders, the Fishin Buddy line may also be mounted to your craft while using included bracket.