One rarely sees the second echo, since most people use auto range and since a depth range set at least twice the depth is needed to see it.

The second echo is sound reflected off the bottom, which is then reflected off the water surface and repeats the cycle. Since sonar measures distance (depth) by time, the second echo takes twice as long to reach the transducer, so it is depicted as twice the depth of the bottom.

What’s under your boat? If you want to understand how your sonar works, just click the link below to get well-guided training with great care!

INTERPRET what you see. 🤔

MAXIMIZE your fishing. 😉

Vassilis is a passionate and knowledgable freediving and spearfishing trainer.