Combine first 5 ingredients in a small saucepan; bring to a boil. Reduce heat, and simmer 15 minutes or until sugar dissolves, stirring occasionally. Strain sugar syrup through a sieve into a bowl; discard solids. Cover sugar syrup, and chill.
Divide watermelon, cantaloupe, and blueberries evenly among 6 dessert dishes. Spoon 1/4 cup sugar syrup over each serving.
