Use a small melon baller to scoop out about 1 cup of watermelon, cover, and set aside.
Cut the rest of watermelon flesh into cubes for easier process.
If you have a juicer, just juice the flesh, otherwise, puree them and pass through a strainer to extract all the seeds, pulp out.
Add 3 teaspoons of gelatin powder to watermelon juice and let it soaks for 15 minutes or so.
While waiting, prepare all other fruits & berries being used. Wash, cut, and slice to your liking.
Prepare 2x 12 oz glasses as jelly holders. You can rim them as well if need now.
Bring 2 cups of water to boil over stove-top or microwave.
Carefully pour the boiled water into the watermelon juice/gelatin, mix it well.
Pour half of the gelatin liquid into one container cup.
Then add half of each kind of fruits into it.
Repeat for the other cup.
Wait till they're both cool down to room temperature, then cover and chill in the fridge overnight.
Serve cold with your loveliest idea of decoration.