Into a pitcher ⅓ full of crushed ice add Gosling's Black Seal Rum, Gosling's Gold Rum, pineapple juice, orange juice, Torani Grenadine Syrup, and Angostura bitters. Churn vigorously until a frothing appears or mix in a cocktail shaker. Strain into a martini glass. Adapted from Gosling's Rum.