Colors, echo strength and hard or soft bottom

The colors on a fish finder are a scale of echo strength. Weak echoes are dim and strong echoes are bright or hot-colored. Exactly which color means strong depends on the palette your unit uses, so the first thing to learn on your own unit is which colors are strong. The bottom is usually the brightest thing on the screen.

The bottom band is not just a line. How thick and how bright it is tells you something about what is down there. A hard bottom, like rock, gravel or packed sand, sends most of the sound straight back, so the band looks thick and bright. A soft bottom, like mud or silt, soaks up more of the sound, so the band looks thinner and dimmer.

Try the control below. It is a drawing of a single column of sound: the echo from the bottom at each hardness, and the faint repeat echo that a hard bottom can cause lower down.

An interactive drawing goes here in the app.

On the water

• Drive over a spot you already know is hard, like a rocky point or a gravel bar, and then over a spot you know is mud. Compare the two bands. Now you have a reference for your own unit.
• A bottom that changes from thin to thick is a hint that the bottom type changed. Hard-to-soft edges are often worth a few casts.
• If your unit has DownScan, look at it side by side with the 2D picture over the same spot. DownScan shows the bottom and anything standing on it in much more detail.

Easy mistakes

• Assuming a bright band means rock. Brightness also depends on your sensitivity setting and depth, so use it as a comparison between spots, not a fixed answer.
• Mistaking the repeat echo under the bottom for a second bottom or a deep hole. In shallow water over a hard bottom, the sound can bounce twice and draw a copy of the bottom at about twice the depth.
• Thinking every unit shows the same colors. Check your palette setting before you compare screens with a friend.

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