How to read a fish finder

Eight lessons with drawings you can move: how sonar works, the screen, arches, the bottom, 2D vs DownScan vs SideScan and more.

How a fish finder works: Sound goes down, bounces back, and the unit turns the wait into depth.
What is on the screen: Depth, speed, temperature, the ruler on the side and the bottom band, one by one.
Fish arches, and why they are arches: Why a fish draws an upside-down U, and why many fish do not.
Colors, echo strength and hard or soft bottom: What the colors mean, and how the bottom band shows what you are over.
2D, DownScan and SideScan: Three ways to look at the same water, and when each one helps.
Structure, thermoclines and bait: What brush, drop-offs, temperature layers and bait look like in the water column.
Sensitivity, gain and noise: Why the screen goes blank or turns to clutter, and how to fix both.
Common misreads: Six things that look like fish or bottom, and what they usually are.