In a blender, combine the yogurt, water and stevia and blend till mixed well.
Cut watermelon pieces ⅛ inch – ¼ inch thick and set aside. Cut plums into small chunks and set aside.
Pour mixture into a measuring cup and pour a small amount of the mixture into each popsicle mold, about ⅛ – ¼ full. Then add a few pieces of each fruit into the mixture and push down with your fingers until the yogurt mixture covers the fruit.
Then pour another ⅛ – ¼ cup of mixture into the mold and again add a few pieces of each fruit into the mixture and push down with your fingers until the yogurt mixture covers the fruit.
Repeat step 5 until each mold is full. What this will look like is yogurt mixture, fruit, push down, yogurt mixture, fruit, push down and repeat until the mold is full.
If you use the popsicle mold I love, it will come with a lid with slits for the popsicle sticks and the actual popsicle sticks. Cover the mold with the lid, and add the popsicle sticks and freeze overnight.
The following day, remove the mold from the freezer and run it under hot water, until you can loosely remove the lid. Continue to run the mold under hot water until the popsicles can pop out of the molds easily.
Store the popsicles in a freezer ziplock bag in the freezer for up to 6 months.