Typically Lowrance units have a 20° cone. So the diameter is close to 1/3 of the depth. You have to keep that in mind when looking for your bait. The bait tends to get behind the cone when the ducer is on the trolling motor. For that reason I mounted one back a ways inside my hull. It is slanted starboard and forward to give me a pic on that side of the boat.
However, with some experimentation you should be able to see your bait with the unit mentioned.