Lonely Water (widely known as The Spirit of Dark and Lonely Water) is a 1973 British public information film made for the Central Office of Information (COI). The film aimed to warn children of the dangers of careless or foolhardy behaviour in the vicinity of water, and was shown regularly on TV for several years during breaks in children's programming. Lonely Water is widely recalled as one of the most memorable and chilling of PIFs. In a poll carried out by the BBC on the 60th anniversary of the COI in 2006, Lonely Water was chosen as the UK's fourth-favourite PIF of all time and the highest ranked one-off production. Dozens of comments attested to the film's power and lasting impact on 1970s children.