Lots of Noise

[banksdd]

hi, I have a cpt-120 connected to an A98. When i am fishing in shallow water where the cpt-120 can see the bottom the reading seems to be ok. I see the bottom and fish, ext. When i am fishing blue water, i.e depth of 3000 plus feet the screen has a lot of noise on it that looks like small dots everywhere. i am not interested in seeing the bottom but just the first 200 feet of the water column. I have attempted to use the noise and gain filters without any success. Is there something i need to be doing when i am fishing in deep water?