I found this recipe online at,

http://www.simplyrecipes.com/recipes/cucumber_lime_mint_agua_fresca/

Ingredients
2 large cucumbers, about 1 lb., trim the ends but leave the peel on and coarsely chop.
1/2 cup lime juice from fresh limes
1 cup packed spearmint mint leaves, remove the woody stems.
1/2 cup sugar (I prefer honey)
Approximately 1 1/4 cup of water
Directions
1 Put all ingredients in blender, add water and purée until smooth.
Place a fine mesh strainer over a bowl and pour the mixture through it,
pressing the solids against the strainer with the back of a spoon to press out as much liquid as possible.
2 Fill a large pitcher with the juice and add some ice.
Serve in a glass with ice, a few sprigs of mint and a slice of lime.