Place water and gelatin in a medium saucepan; mix well. Let stand for 2 minutes. Add sweetened condensed milk and coffee granules. Heat over medium heat, whisking constantly, until coffee is dissolved and mixture reaches a gentle boil.
Remove from heat; place saucepan in the freezer for 15 to 20 minutes, stirring mixture every 5 minutes until it is thick and cold. Transfer into a large bowl.
Whip cream in small mixer bowl until stiff peaks form. Fold whipped cream gently into coffee mixture. Spoon mousse into 5 individual glasses; refrigerate for 2 hours. Serve.