In this hypothetical case, outside the paramecium cell, there is water with a high concentration, which probably is referred to as solute concentration. In this case, the interior of the cell (paramecium) probably has a different concentration of solute, which led to an osmotic process where water passes through the semi-permeable membrane. Water flows towards a place with less water and more solute.
The vacuole as its name states is contractile and is in charge of regulating this process, it expands when water enters the cell, and it is contracted when expels the excess water. So if this mechanism fails, water will enter unregulated to the cytoplasm of the paramecium causing the cell lysis. On the contrary case, where water flows outside de cell, this, in turn, would lose practically their whole cytoplasm, causing dehydration, contraction, and collapse of the cell.