Submerging a red blood cell in distilled water will result in

Submerging a red blood cell in distilled water will result to the expansion of the red blood cell which may lead to bursting (hemolysis). This is because the red blood cell has a hypertonic solution and the distilled water is a hypotonic solution and in order to reach an equilibrium in terms of solution concentration the distilled water will move into the red blood cell making it expand and maybe even burst.

Distilled water is an illustration of a lower osmotic pressure than a particular fluid solution, meaning it has less solute in it compared to a red blood cell. The red blood cells would "want" to be in a normal contraction, which would allow water to leave and exit the red blood cell, meaning the red blood cell would stay normal and not shrink or stretch. In a hypotonic atmosphere, water would blast into the red blood cell in an attempt to reach the symmetry, which would cause the red blood cell to lengthen, and perhaps even burst.