I can always see fish on the screen, but in reality I don't believe they are really there. I have one on the front of my boat, and one on the back. Neither one show the same amount of fish at any one time.
honestly, good fishfinders are expensive. i had some peice of cr*p hummingbird on my first boat. than i upgraded i bought two lowrance hds 10's. the difference is night and day. you get what you pay for. if you want a fish finder that works than drop some cash.