Combine 3 heaping cups of cubed watermelon, 1 heaping cup of strawberries, and the zest and juice of 1 lime in a blender. Blend until smooth, about 1-2 minutes.

Taste the mixture and adjust with more lime juice or a natural sweetener if desired. Blend again for 10 seconds.

Pour the mixture into popsicle molds, filling them three-quarters full. Cover with lids and insert sticks. Freeze for 3-4 hours until solid.

To remove, run warm water on the outside of the molds for a few seconds and gently wiggle the sticks to release the popsicles.