Fish finder question

[mbsurf]

I have the Mark 4 shooting through the hull. I have seen the exact same "60 ft freak out" reading earlier poster mentioned numerous times. I just shut it off and turn it back on. It happens almost every trip. This is my first first finder, so for $200 with GPS I'm pretty impressed. I shot this picture the other day, which I presumed to be the fabled fish arches. Anyone with experience interpreting the greyscale please chime in. Looked promising to me!