Hello Jake I am also using a Eagle Depthfinder..the book that I recieved with mine says to lower it to 20% if your just slowly drifting..I figure that is just about the speed of a tube. I have only had mine out about 6 times and with it set on 20% have had no problems ..I think my book says if you have it set to high and your only drifting say if a fish swam into the sonar it would come back as a streak rather than a arch or a fish symbol.

Keith