Add the lemon juice, lime juice, orange juice, simple syrup and water to a blender.
Fill the blender with ice until about the 12 ounce mark.
Pulse the blender until the mixture is smooth, without any big ice chunks. If you need to, shake or stir the mixture with a spatula. If the blender is getting stuck, you can add a little bit more water.
Pour or use a spoon to add the slush to your serving glasses.
Garnish (optional)
Stack up your citrus slices on top of one another and cut a slit from the center out through the edge of the peel.
Making sure the slit is lined up on each slice, twist the slices together.
Rest the twisted slices on top of the drink. The slush should be thick enough that it will stay on top with no problem.
Serve the drink. You can even serve it with a spoon if you'd like!