Slice a cucumber into thin rounds and soak in ice-cold water for 10-15 minutes.

Peel and chop another cucumber into small cubes to yield about 1 cup.

In a blender, combine cubed cucumber, sweetener, mint leaves, and 1 cup of water. Blend until smooth.

Strain the mixture using a fine-mesh strainer to extract the juice.

In a large pitcher, mix the strained cucumber juice, lime juice, remaining water, and black salt.

Serve in glasses with soaked cucumber slices and ice, garnishing with lime rings and extra mint leaves.