what you actually see on a fishfinder

[cause]

What you see on a"fishfinder" is a trompe l'oeil.

had to look that one up

Trompe-l'œil (French for "deceive the eye", pronounced [tʁɔ̃p lœj]) is an art technique that uses realistic imagery to create the optical illusion that the depicted objects exist in three dimensions. Forced perspective is a comparable illusion in architecture.