Shallow water with a hard object return! The right transducer is picking up the reflected sound waves from the left side. I get it quite often in small shallow creeks, especially when the water surface is very calm.
Also just occured to me looking at the image...... Do you have your transdcuer mounted on the left side of your motor? It could be reflecting off the motor and thats why the right side is picking up the returns from the left.
Robert