I have an H-Bird Matrix 47 system. I bought an add on to use the castable sonar. I have not had any problems with it and it has found fish. One time fishing with another boat we were having a slow period catching walleyes on Lac Seul, so I fired up the castable and did some seeking around. I got a good return from a spot about 6 ft. from the other boat. I told my buddy that there were fish right under the sonar but he didn't want to move his float rig. (I don't rig my sonar with any bait or hooks for snagging reasons) I then cast a jig and a leech right under the sonar and BAM! caught a nice 20" one. Boy did that make the other guys want to fish there.
Anyway, the castable does work, just doesn't have real high resolution.
There is a thin line between fishing and standing on the bank looking stupid,,,, yea, but as long as that line is in the water who cares?!