Locating the Thermocline, on lowrance 5x elite

I think I know the answer to my question but want to check without having to dive in. I set the surface clairity to low and I see a red block at about 5 feet never goes away. If I set surface clarity to high it is mostly gone. Same for sensitivity, up over 55 I see it strong but down around 36*40 it is mostly gone. This lake was 52-54 degrees and tea colored water on a bright sunny day. I keep seeing fish arches just above this red blob running across the screen but I never caught a fish at that dept or above. Was this the thermocline?

I would not think it is a thermocline. We usually see a thermocline when the water temps are much warmer, im not sure what you mean but it sounds like you are describing surface clutter if it is at the top of your screen and gets worse as you increase sensitivity. Not sure but i think thats what you are saying.