Bring water and sugar to a boil in a saucepan; stir until sugar is dissolved. Set aside to cool.

Blend watermelon a little at a time in a blend. Pour in a large bowl and continue till all watermelon is blended. Add lemon juice and sugar mixture; stir together.

Pour watermelon mixture into a 9x13 pan pan. Cover tightly with plastic wrap and place in the freezer for 7 hours, or overnight.

Remove from freezer and mix around with a fork to break it up. Serve with an ice cream scoop into bowls.