Add the water to a small heavy saucepan and bring to a boil. Remove from the heat. Stir in the couscous, 1/4 teaspoon of the salt, and cover. set aside until the liquid is absorbed about 10 minutes. Fluff the couscous with a fork and transfer to a large serving bowl, spreading and fluffing the grains again. Set aside to cool for about 15 minutes.
Meanwhile, zest the limes until you have 2 teaspoons zest. Squeeze the fruit until you have 3 tablespoons of juice. Place the zest and juice in a small screw-top jar and add the olive oil, honey, the remaining 1/4 teaspoon salt, and pepper. Shake vigorously until the dressing is amalgamated.
Once the couscous has cooled, distribute the watermelon, cucumber, and mint across. Drizzle the dressing across and gently toss to combine. Season with pepper to taste.
To finish, toss again, top with the crumbled feta and the mint leaves for garnish, and drizzle with a touch more olive oil.
Servings 6
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.