Combine first four ingredients in large bowl. Cover and chill
for 30 minutes. Process watermelon mixture in a blender until
smooth and return to bowl. Sprinkle gelatin over cold water in
a saucepan. Let stand 1 minute. Cook over low heat, stirring
until gelatin dissolves (about 2 minutes). Add to watermelon
mixture, stirring well. Add whipping cream and beat at medium
speed with an electric mixer until fluffy. Pour mixture into
freezer container of ice cream maker and freeze according to
manufacturer's directions.