1. Add the fish glue powder into the cold boiled water and stir well, then melt in hot water.
2. Add white granulated sugar to the pulp of watermelon and stir into a blender to make watermelon juice.
3. Pour the fish glue powder into the watermelon juice and stir well.
4. Pour the watermelon juice into the watermelon shell.
5. In order to make watermelon jelly look more realistic, you can put some watermelon seeds on it.
Refrigerate in the refrigerator for about 3 hours and then solidify.