40 Olympic-sized swimming pools. That’s the amount of wastewater that is being discharged every day into the sea around the Canary Islands. There are 400 waste discharge points on the islands and only a quarter of them are legal. There has been no proper planning for wastewater treatment despite the tourist boom and an increased population on the islands over the last few decades. Most of the islands’ wastewater is untreated or barely treated before being ejected into the sea through sometimes illegal channels. The authorities are trying to accelerate the rollout of state-of-the-art purification plants, but the situation remains very worrying. Our team went to the popular tourist island of Tenerife to find out more. Report by Armelle Exposito, Victoria David and Sarah Morris