For the jelly
In a pot, mix the water and sugar and boil until the sugar melts. Then, let the syrup cool.
Plunge the gelatin sheets into water, until soft and flexible.
Pour the syrup into the blender, along with the watermelon, and blend.
Strain the mixture with a chinois.
Place the mixture in a pot and heat it over low heat, until it is almost brought to boil.
Remove from heat, add in the gelatin (after squeezing it well with your hands) and the lime juice, whisk until homogeneous and sieve with the chinois.
Let it cool to approx. 30 degrees C.
Divide it among glasses of 150 gr. each and refrigerate until set.
Mix all ingredients for the topping and garnish the jellies.