1. Peel the mangoes and remove as much flesh as possible from the pits. Dice the flesh into large pieces.
2. Place the mango pieces into a blender along with the sugar, lime zest and juice, ginger and water. Purée the mixture until liquefied to form the granita base. This makes about 5 cups.
3. Strain the granita base and place in a large baking dish. Freeze, stirring every half-hour or so until the granita is frozen. To serve, shave the granita, raking the tines of a fork across the surface to break up the crystals. Serve immediately.