In blender, blend watermelon cubes and jalapeno pepper until completely smooth. Pour mixture through fine sieve set over pitcher.
Add lime juice, salt, pepper, fish sauce, horseradish, and hot sauce, to taste, to pitcher; stir to combine. Taste and adjust seasoning as needed. Add vodka and stir.
Line rims of four glasses with lime juice from lime wedges; dip in chili lime salt poured on plate. Carefully put ice in each glass and divide Watermelon Bloody Mary mixture evenly.
Add garnishes, as desired, by skewering watermelon wedges, prosciutto, cucumber, jalapeno, and green olives. Place garnishes in glasses and serve.