If you want to make this as a pitcher, I'd suggest making simple syrup ahead of time rather than using sugar (as noted in post above). So eg for 8 glasses, put ½ cup (80g) sugar and ½ cup (120ml) water in a small pan and stir to dissolve the sugar. Bring to a gentle simmer and then leave to cool before using. You can add mint leave to infuse in there as well (remove before using). Then use juice of 4 limes, the simple syrup and some crushed mint leaves (around 60 leaves) along with 12oz (360ml) rum. Add 1 ½pints (720ml) pomegranate juice. Divide between 8 glasses filled with ice, and top each up with sparkling water.