Bring the water and sugar to a boil in a saucepan, stirring to dissolve sugar. Add the hibiscus flowers, turn off the heat and let the mixture steep at least 15 minutes and up to 1 hour for a stronger color and flavor.
Strain the syrup into a metal or glass bowl and chill in the refrigerator until super cold. Pour the syrup into a large (at least 4-cups) liquid measuring cup or bowl with a spout. Stir in 1 cup cold water with the lime zest, juice and salt.
Pour into popsicle molds and freeze until solid.
Leave the popsicle mold at room temperature for about 10 minutes to make it easier to get the pops out. Or run it under warm running water for a few minutes. Wrap the popsicles in plastic and store in the freezer.