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.

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https://freedivegreece.com/academy/sonar

INTERPRET what you see. 🤔

MAXIMIZE your fishing. 😉