Urine-indicator dye is a mythical substance that is supposed to be able to react with urine to form a colored cloud in a swimming pool or hot tub, thus indicating the location of people who are urinating while they are in the water.
Urine-indicator dye is a mythical substance that supposedly reacts with urine to create a colored cloud in a swimming pool or hot tub, thereby indicating the location of individuals who are urinating while they are in the water.