Final answer:
No net movement of water molecules occurs when two regions become isotonic, as equilibrium is achieved and osmosis ceases.
Step-by-step explanation:
There will not be a net movement of water molecules when two regions have the same water concentration. At equilibrium, although water molecules continue to move across a semipermeable membrane in both directions, there is no overall change in water volume on either side because the rate of water movement in one direction is equal to that in the opposite direction. This state is known as isotonic, where no net osmosis occurs since the solutions have equal water potential. Osmosis typically happens when there is a concentration gradient, with water moving from an area of higher to lower concentration until equilibrium is reached.