Odd Depth Sounder Readings

[S/VSkylark]

While at the boat this weekend, the wind had pushed quite a bit of water out of the river and we were all sitting rather low. Thought I would check the depth and see how close I was to the bottom using the newly (November) installed depth sounder. The last 10 times I had used it, the depth readings were right in line with the boat next to me. This weekend however, I was getting a readings from 200 feet to 2 feet with it never stopping on any number, just kept showing random depths. Any idea what would cause that? I am thinking it's either time to scrape the hull as growth is throwing off the transducer signal or, the transducer got damaged some how with the temps in the teens. I am leaning more toward choice A, but any info would be appreciated. Thanks.

[promax]

my raymarine unit will do that in very shallow water

[gonesail]

turbulance can cause depth sounders to give false readings.

[John A]

Depth sounders don't indicate depth!
They measure the time it takes for a signal to traval from the send unit, bounce off of something and return to the unit.
It could be a dirty send unit, shollow water, or turbulance.