In a high-speed blender, add whole limes and water. Pulse 6 to 8 times. (Note: Don’t pulverize limes or the end result might turn bitter.)
Pour mixture into a pitcher using a fine-mesh strainer to remove pieces of lime. Using the back of a spoon, press lime pieces to release any extra juice. Discard pulp.
Add strained juice back to blender with condensed milk, sugar and if desired, ice. Blend 1 minute.
Serve over ice with sweetened condensed coconut milk for a final touch of flavor.
