Add peach slices and diced mango to the ninja creami pint. Gentle stir them to try to evenly combine the mango and peaches (to prevent a distinct mango layer and peach layer). Pour coconut water over, fully submerging the fruit pieces (do not go past the max fill line).
3/4 cup peach slices, 3/4 cup diced mango, 1 cup coconut water
Cover the ninja creami pint with its lid, then place in the freezer for at least eight hours.
Let the Creami pint set on the counter for 10 minutes prior to spinning, or run the sides under tap water. Place the pint in the Ninja Creami and spin on the "Sorbet" setting. Respin as needed (I find 1-2 respins are generally needed).