In a blender, puree watermelon chunks until you have acquired 8oz of juice. Add in ¼ jalapeno and pulse until liquefied (more or less jalapeno depending on desired heat).
In a shallow dish, mix coarse salt, chili powder, and cayenne pepper to desired heat.
Rub rim with lime wedge and dip in salt mixture.
Add 4-5 ice cubes to glass.
In a cocktail shaker, add all ingredients and shake vigorously.
Strain cocktail mixture over the ice in glass
Top off with a bit more cucumber mix (optional)
Top with sliced jalapenos and watermelon wedge