On August 5, 2019, My organization Champ Search, aboard our research vessel "Kelpie" ventured out on an expedition covering 30 miles of Lake Champlain on both the New York and Vermont sides of Lake Champlain, scanning with our Dragonfly Pro-4 Chirp Sonar System. During this time, the gas gauge on the boat plummeted down with great significance and we decided turned around to head back to port. During this time, I was traveling around 45 MPH and noticed two unusual anomalies on the on the sandy bottom of the Lake at approx.165 ft. We were urgent to get back to avoid running out of gas and I couldn't see the images clearly on the screen due to the sun glare, but I snapped a screenshot on the sonar as they looked very different from the 56 other images we had seen previously that day.
The next morning I decided to go over each of the sonar images and came across that particular and peculiar screenshot and enlarged it. To my amazement, I was in complete shock as all of the eyewitness descriptions (particularly the on-land sightings of the whole body of Champ) flooded into my head, as well as the head and neck sighting that I had experienced on the evening of July 24, 2014.
The animal appears to be hunkered down on the sandy bottom. My idea is that they both heard the sonar and because we were traveling at a fast speed, dove to the bottom, very similar to the account of a Japanese crew in 1993 that picked up and chased a large target that went to the bottom and appeared to be avoiding the sound of the sonar.
Since these animals have echolocation capabilities, it leads me to believe they have a very sensitive hearing range.