Cut the watermelon into 1 inch size cubes. You will need 3 cups of cubes.

Freeze the cubes in a bowl or plastic bag for 30-45 minutes (or until they are frozen solid).

Place half of the frozen watermelon cubes in a blender (or a food processor). Blend it on the medium setting for 45 seconds to a minute until it becomes a bit grainy. If the watermelon still seems chunky blend it a little longer.

Next add half of the yogurt to the blender. Turn the blender back on to a lower setting and allow the two ingredients to blend until the consistency becomes creamy and smooth.

Pour the soft serve into a container that has a lid then repeat the steps with the remainder of the watermelon and yogurt.

Cover and freeze for an hour then it is ready to serve.