Lightly grease and flour 2 (9-inch) round cake pans.
Combine first 3 ingredients in a large mixing bowl. Beat on low speed with an electric mixer until blended; add butter, eggs, and water. Beat on low speed 30 seconds. Increase speed to medium, and beat 2 minutes. Pour batter into prepared pans.
Bake at 350° for 20 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes.
Place coconut on a jellyroll pan. Bake at 350° for 8 minutes or until golden, stirring every 3 minutes. Cool completely.
Remove cakes from pans; cool on wire racks. Slice each layer in half horizontally, creating 4 layers.
Blot moisture from pineapple and mango with paper towels. Gently toss fruit together in a medium bowl. Beat cream, sugar, and vanilla in a medium bowl until stiff peaks form. Spread 1/3 cup whipped cream, 1 cup fruit mixture, and 1/3 cup toasted coconut between layers. Frost cake with remaining whipped cream, and sprinkle with toasted coconut. Chill until ready to serve.