Spoon yogurt into the bottom of 3 to 4 popsicle molds, being careful to not let it drip down the sides of the molds. Place uncovered molds into the freezer for 10 minutes. While the yogurt layer is firming up, blend together the pineapple and coconut water until smooth. Remove molds from the freezer and spoon the pineapple mixture in. Add caps or popsicle sticks and place back in the freezer for 4-6 hours. Run under warm water to release the popsicles from the mold when ready to eat.