Think about it Chuck; at 237 feet of water the 20 degree 200kHz beam would be about 83 feet wide. If he were passing by some trees (or some other tall structure), the leading outside edge of the sonar beam would start picking up weaker sonar returns first before you would see the stronger sonar returns when the boat was more directly over the trees and they were more centered, followed by weaker sonar returns again as the trailing outside edge of the sonar beam was still picking up the trees.
We don’t know his unit settings and certainly do not know what could be under the water he was on.
Interesting screen snapshot though.