This is a drawing of the interior of Neptune.
Click on image for full size
NASA
The Structure of Neptune's Interior
There is no surface to the giant planets, only a gradual transition from the atmosphere, as depicted in this drawing. Therefore the giant planets do not have strict layers, as the terrestrial planets do.
Ice begins forming in the atmosphere of Neptune and keeps increasing until there is slush, and then solid ice. There is not much difference between the atmosphere and the ocean, unlike the earth, where there seems to be a surface.
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