Fill a highball glass with cubed ice and set aside.
Add the small-batch spring water into a shaker with cubed ice, and shake until well-chilled.
Dump the ice from the highball glass, and replace with 3 large ice cubes.
Strain the small-batch spring water into the highball glass.
Top with the sparkling water.
Float the distilled water over the top, and gently stir.
Garnish with a watermelon slice.