Spain’s public swimming pools are being hit by a revolting and unhygienic social media trend in which children and teenagers deliberately defecate in pools so they can film the ensuing chaos for views and likes online.

The trend, known as the reto marrón (“brown challenge”), is causing widespread outrage and significant damage at outdoor pools across the country, local media report.

Although fines can reach €20,000, in addition to substantial compensation claims and multi-year bans, Spanish media are reporting new cases almost daily.

There is no central record of incidents at the mostly municipally run pools, but there were around 300 last year and already “hundreds” so far this year, broadcaster Cadena Ser reported.

Catching perpetrators in the act is difficult, however. Some reportedly bring faeces in plastic bags hidden in their swimwear and empty them into the water, the newspaper La Razón reported.

In the northern Spanish city of Burgos, however, fine proceedings have now been launched against the parents of four children aged between 11 and 13, the city administration confirmed to dpa. They were seen by an adult releasing faeces in the El Plantío pool. The man immediately alerted police, who took down the children’s details.

The parents now face fines of €3,000 ($3,500) each and compensation claims from the municipality for cleaning and disinfecting the pool. If the water has to be replaced, this can cost several thousand euros. The perpetrators themselves also face multi-year bans.

Burgos mayor Cristina Ayala stressed that proceedings would be pursued “to the very end.” She said it was already the sixth such case at the city’s outdoor pools this year.

Andrés López, a psychiatrist and coordinator for mental health in the Osuna health district, said in an interview with Cadena Ser that this type of behaviour could stem from emotional problems in a particularly vulnerable group such as teenagers and young adults.

He said they use social media to seek recognition or to combat feelings of loneliness. López stressed that social media have certain addictive mechanisms that encourage a bandwagon effect, leading people to imitate this kind of antisocial behaviour.