In a small pan, combine vinegar, sugar, water and salt; cook over medium heat, stirring, until liquid boils and sugar is dissolved.

Remove from heat and let cool to room temperature.

Peel or score cucumber, if desired and cut lengthwise into quarters; then cut quarters crosswise into 1/8-inch-thick slices.

Place in a serving bowl, pour marinade over cucumbers; stir to blend.

If made ahead, cover and refrigerate for up to 2 hours.

Top with peanuts before serving.