Thermoclines usually show up as a 1-3ft band of scattered marks, in a line across the screen, and well below the surface. So ...either of the lines at 20ft or 30ft "could" be it.
My experiences tell me that the heavy markings from 0ft - 15ft are surface clutter, or too high a setting on surface clarity. The "pole" shaped vertical marks are reminiscent of cross talk interference, or possibly the unit going bad ... but for sure, since I don't have either of those units.
... cp