Urine-indicator dye

Urine-indicator dye is a fictional substance which is supposed to be able to react with urine to form a colored cloud in a swimming pool, thus indicating the location of people who are urinating while they are in the pool.^[1] Rumors of this chemical's existence go back at least as far as 1958.^[1] A 1985 biography of Orson Welles describes such a dye as existing in 1937,^[1] and references to the substance can be found through popular culture over quite a lengthy time period. However, such a dye does not exist, and although a chemical could be manufactured that would react with urine, it would be difficult to prevent it from reacting to other organic substances present in pool water.^[1]

A few companies capitalized on this urban legend by creating professional pool signs that warned that the pool was indeed being monitored with the chemical called "wee alert" or a similar catchy name.

The 2010 film Grown Ups and the 2011 film Take This Waltz both feature scenes in which the chemical is featured as if it were real.

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