Remove the watermelon pulp from the skin. Put the red pulp in the blender and mix vigorously until the melon is liquid. If there are seeds in the pulp, just mix in.
Then pour through a hair sieve and press the juice through the sieve with a spoon. Just throw away the seeds and larger pieces. Put the resulting juice in the refrigerator for an hour.
In the meantime, peel the bananas and cut them into small cubes. Then put a small ball of vanilla ice cream in a glass and spread a banana over it. Pour the watermelon juice over it and serve with a spoon and a straw.