Put the peaches in a food processor or blender with the lime juice, sugar, and salt, and process to a very smooth purée.
For each drink, pour 6 oz. (3/4 cup) seltzer water over ice into a highball glass. With a bar spoon, stir in 3 Tbs. of the peach purée. Garnish with a peach slice.
Photo: Squire Fox