It depends on how you interpret "toward the water".
The x-axis represents time in seconds.
The graph shows the stone rising from 0 to 0.5 seconds and then falling the rest of the time.
If "toward the water" means from the time it left her hand, then the answer is 0 to 1.5 seconds.
If "toward the water" means the stone's downward path, after rising at first, then the answer is 0.5 to 1.5 seconds.