ALTHOUGH THE WATERLEVEL IS UNDER THE GROUND, DUE TO THE INTERFEROMETRIC SHIFT YOU SEE THE WATER SOMETIMES ABOVE THE GROUND LEVEL. SOMETIMES THE EYE TROUGH THE BRAIN DOES NOT CALCULATE CORRECTLY THE DISTANCE BETWEEN THE OBSERVER AND THE GROUND/WATERLEVEL. IN THIS CASE THERE IS AN INTERFEROMETRIC GAP THAT MAKES YOU THINK THAT THE WATERLEVEL IS ABOVE THE GROUND LEVEL.