I'm not much of an electronics guy, so the technical data about hertz etc means nothing to me Smudge, but as mentioned above, SideVu (Garmin) or side scan is very useful for identifying where reef meets sand or other structure.
That makes it an excellent tool for slowly fishing around coastlines, with lures in particular I guess, though it would be helpful for positioning at anchor to strayline with berley.
I don't use it in deeper water over sand - usually just use the traditional view to see sign.
The main thing to remember with side scan is that the top of the screen where the black line starts is the stern of the boat, so everything you see on screen (out either side) is what you've already passed. No point seeing a rock and casting towards it as if it's what is actually beside you, as it will be well behind you by that point.
As i understand it, the black top to bottom 'stripes' on the screen represent the water depth on the distance scale from the white line in the middle, which is your transducer; of course the distance out to the side the various objects are is measured by the scale along the bottom of the screen too (in feet or metres depending on your settings).
So if it's 8m deep where the boat is, the black stripe on the left will be 8m on the scale to the left of the white stripe, and the black stripe to the right will be 8m on the right scale.
Once the beam hits the bottom it turns out to each side, like a torch light - which creates the 3D effect that you see - shapes and the shadows behind them.
This screen shot is from a helpful YouTube explanation i've watched a few times.
I think if you have a touch screen (which I don't), when in side scan mode you can touch a point on the screen e.g. a bit of reef as a 'mark' and then use that on the chart view to drift over later or fish back to with bait.
On YouTube I have seen it used by estuary fishos in northern Australia to identify individual barramundi (and in one case a huge shark) but I'm not sure if they have special transducers or use a particular resolution. They see the fishes' shadows on the bottom.
that may be more effective in shallow water like an estuary than in 20m+?
I understand you can use it to see if a channel marker has kingies under it - which would be cool on your run up the harbour before you hit the bar.