Your transducer is probably mounted in a location where it's getting
a lot of water turbulence. Transducers don't like air bubbles.
You can try lowering it a little. If you have an aluminum boat, you don't
want it directly behind a rivit, or anything on the hull that will churn up
the water. Also, you don't want the transducer too close to your prop.
Also, you can increase your noise filter setting.
I'd move the transducer first and see if that helps.