The bottommost layer has no water below it, so no buyoncy provided, so it does not move upwards because it would lose the upwards force of the seabed, and could not support the weight of water above it.
The next layer up, resting on this layer, is held up by this bottom layer, but since the bottom layer cannot move upwards, neither can this layer, since if it were to do so it would lose the buoyancy and upwards force of the bottom layer and therefore would not be able to hold up the layers above.
The same can be said for the next layer up, if it were to rise it would lose the buoyancy of the lower layer, and therefore has no force to hold up the layers above, which would then push it down.
This applies for all the layers, aside from the top layer, which has no water above it, this topmost layer of molecules can float away, and they do, in the form of evaporation, which leads to rain.
Even if you were to somehow come to the insane conclusion that water can magically fly and matter should fly appart, then you would have to explain the fact that this magic flying water problem applies both to the RE and FE models, since the UA performs the same function as the gravity of RE.