This superb little fish/depth finder doesn't pretend to be top spec but it does exactly what it says on the box. It has a specified range of 100ft and I would say that is pretty accurate, it gives me somewhere between 30-40yds before the picture either breaks up or fails to register at all. It also claims to read up to 100ft in water depth but I can't verify that as I have never used it in water over 30ft deep.
When in range it has a great little LCD screen at the butt of your rod and shows up fish and bottom features superbly and displays the water depth without all the hassle of continually lobbing a plummet in and out of the water creating disturbance. Whilst this does show up large fish or shoals of smaller stuff, I mainly use this for finding shelves, ledges, drop-offs, plateaux and other such bottom features. It even highlighted an unusual feature that turned out to be a sunken dinghy. Of the fish it spots, pike and large carp in particular show up really well and given that pike tend to lie motionless in known ambush points, its great for spotting their holding places. Its simple to use, attach the small sonobuoy to your line and cast it out, switch on the receiver, then slowly retrieve the transmitter (RF45) as it floats on the surface and see what happens on the screen. Make a mental note of where the bright yellow transmitter is as features show up. Its so simple to use. The transmitter is a sealed unit that lasts for about 400hrs of in-water use but cleverly switches itself on and off when its placed in and taken out of water. Mine has lasted me 3 whole seasons and is still going strong but suspect I will need to replace it soon. The receiver unit takes a standard watch battery and again, not needed to replace one yet.
I can think of only two minor points:
1. In medium/fast flowing rivers the RF45 transmitter tends to get easily swept along in the surface flow and needs faster retrieval to maintain its line, which in turn can degrade the quality of the information you get back.
2. In the summer the pike go mad for these and attack them like crazy so use them with a trace or you will lose a very expensive RF45 transmitter and they are about £30 to replace.
I was dubious at first when I first saw one used but it took just a 5 minute demo on our local syndicate lake to convince me this is a damn useful tool to have and it takes up very little room in your tackle box. Give it a go ... you will become a convert and its a great gadget for showing kids what is going on under the surface.