Place the pineapple compote and the condensed milk in the fridge for an hour. Dissolve the jelly in the water and set aside to cool. Beat the condensed milk until it becomes creamy and add 1 cup of the compote syrup. Add the pineapple, after cutting it finely. Last, add the cold jelly. Place the mousse into a deep glass bowl or into individual bowls and garnish with pineapple. Place in the fridge for 3-4 hours.