Add light rum, dark rum, banana liqueur, triple sec, orange juice, and pineapple juice.
Shake vigorously for about 15 seconds until well chilled.
Strain into a tall or hurricane glass packed with fresh ice.
Slowly pour grenadine down the side of the glass so it settles at the bottom for a layered effect.
Garnish with an orange slice and a maraschino cherry. Serve immediately.
Notes
Use fresh juices for brighter flavor. For a lighter drink, reduce the rums and add more juice. For extra depth, float a splash of dark rum on top. Crushed ice gives a smoother, beach-bar feel.