Place 4 cups thinly sliced cantaloupe (about 1 1/4 pounds) 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 cantaloupe to infuse. Stir well and strain, discarding the cantaloupe. For serving, add fresh cantaloupe slices for garnish and plenty of ice. The infused water will keep refrigerated for up to 2 days.