Place 4 cups thinly sliced pineapple (about 1 1/4 pounds), 5 sprigs mint (lightly crushed) and 8 round slices ginger (smashed) in a pitcher. For still infused water, add 2 quarts of water. For sparkling water, add 1 quart of seltzer during prep and a second quart just before serving. Refrigerate 2 to 4 hours to allow the ingredients to infuse. Stir well and strain, discarding the solids. For serving, add fresh pineapple, mint and ginger for garnish and plenty of ice. The infused water will keep refrigerated for up to 2 days.