We have to remember that distance in the SI image is
"Range away from the xducer."..
This means that a SI Range setting of 25m would be displaying all the Range (away from the xducer) to all the points 25m away from the xducer within the SI beam slice...
If your "target" area is, indeed within this 25m Range (away from the xducer)...regardless of the actual water's depth ...then the display will show the echoes detected within this 25m "range away from the xducer"....
If your interference problem is from overlapping beams (crosstalk)...the interference may still show on the display ...because the SI Range setting is not "stopping" the beam from going out past the SI Range setting...it's just telling the unit not to "display" echoes out past the SI Range setting...
Rickie