Place the chilled watermelon cubes into a blender and puree until very smooth (about 20–30 seconds). Strain the puree through a fine mesh sieve or cheesecloth into a bowl or measuring cup to remove pulp and seeds. You should yield roughly 1 to 1 1/4 cups of clear juice.

Make cucumber-agave

In a small blender or food processor, combine the peeled chopped cucumber and 2 tablespoons agave nectar. Puree until smooth (about 15 seconds). Strain the cucumber puree through a fine mesh sieve, pressing with the back of a spoon to extract as much liquid as possible — you should get about 1/3 to 1/2 cup of cucumber-agave liquid. Taste and add up to 1/2 tablespoon more agave if you prefer sweeter.

Combine citrus with juices

In a measuring cup, stir together the fresh lemon juice (1/2 cup) and fresh lime juice (1/4 cup) with the strained watermelon juice and strained cucumber-agave mixture. Stir to combine and taste — the combined juice should be bright, slightly sweet, and balanced with acidity. Adjust sweetness with additional agave if needed (optional). Chill in the refrigerator briefly if not using immediately.

Mix the Martini

Fill a cocktail shaker with the ice (about 2 cups) until roughly 3/4 full.

Add 6 oz cucumber-infused vodka and the combined watermelon-cucumber-citrus mixture to the shaker. If you prefer a stronger martini, add the optional extra chilled vodka (1 oz).

Shake vigorously for 12–15 seconds until the shaker is very cold to the touch and slightly frosted. This ensures dilution and chilling.

If you prefer a clearer martini, double-strain the mixture into a chilled martini glass using both the shaker strainer and a fine mesh sieve to catch any remaining pulp.

Garnish & Serve

Optional rim: If using a rim, wet the glass edge with a lime wedge and dip into coarse salt or tajín (1 tsp).

Garnish with a thin watermelon wedge or a single watermelon ball and lay a thin cucumber ribbon along the inside of the glass or threaded onto a cocktail pick.

Serve immediately while cold.