Two things - first, I have the mini that I bought for my 2 man boat that I use on smaller waters. It is 9V powered, so out of curiosity I took it down to my dock, turned it on & dropped the probe. Now I have several brush piles planted, so the fact that bream & crappie were present was not a surprise. But what shocked me was the 2 Cormorants that swam up & kept pecking the speaker.
Second, I take a trip every year to the Classic & the FLW Cup. I asked the question to every Pro I could. The universal answer was that if it did nothing else, it masked the trolling motor & graph emissions. One of two brothers even said, that just because you don't see it on a Pro's boat, don't think it's not mounted in a compartment, with a wink....
Take a kid fishing.