Some swear by sensitivity adjustments, garmin doesn't have that at least on my model.
Hey guys on the Humminbird it's not a bad unit my dad has the 997c on his boat,this is my experience with it,the SI is cool but you have to go slow to use it,and the way they made the plugs in the back,rough water will knock it out,we tape his to stay in, HB says there's nothing wrong with it maybe they changed that on the new one's,but it still is a good unit,i recommend a thru hull transducer for it though,the transom mount one is huge and throws off it's own wake which reduces readings at speed,also if your used to a Garmin the learning curve is much greater on this machine.