In a blender, combine watermelon, frozen strawberries, and a splash of coconut water. Blend until smooth, adding more coconut water as needed to adjust the thickness. The puree should be pourable like a smoothie. Set aside.
Clean the blender and make the piña colada mix. Blend together pineapple, ice, coconut water, coconut cream, and rum.
To assemble, fill the cocktail glass with about 1/3 tiger's blood puree. Use a spoon to gently layer the piña colada mix on top, creating two distinct layers. Then, move the spoon in an up-and-down motion a few times to create a visually appealing "lava" effect.
Garnish with watermelon and serve!