Put frozen mangoes and bananas in the bottom of the blender.
Add Chia seeds and protein powder (if using) next.
Peel cucumber and cut into 1” slices.
Top with spinach. And press down before blending.
Add water either before or after the spinach.
Blend well until all the spinach is completely blended and not chunky. When you think it is blended enough, let it mix just a little bit longer for smoothness.