8 oz of 7-up soda (or Sprite)
2 oz of Light Rum
1 oz of Lime Juice
2 oz of Passion-fruit Syrup
1 oz of 151 proof rum (or overproof rum)
Shake all ingredients except 151-proof rum in a cocktail shaker with ice. Pour into a hurricane glass and float the 151-proof rum on top. Drink through a straw from the bottom up.