Combine the water and sugar in a small saucepan over medium heat, stirring just until the sugar dissolves and the syrup is clear, 2–3 minutes. Let cool to room temperature, about 10 minutes.
Add the diced mango, lime juice, salt, and the cooled syrup to a blender. Blend until completely smooth, 45–60 seconds.
Optional: For extra-smooth pops, strain the puree through a fine-mesh sieve into a bowl, pressing to extract as much liquid as possible.
Pour the mixture into 10 (3-ounce) popsicle molds, leaving about 0.25 inch of headspace. Tap the molds on the counter to release air bubbles.
Insert sticks according to your mold’s design. If your mold requires slushy support, freeze 1 hour, insert sticks, then return to the freezer.
Freeze until solid, 4–6 hours, until the pops release cleanly and feel firm.
To unmold, briefly run warm water over the outside of the molds for 10–20 seconds, then gently pull out the popsicles and serve immediately.