Submarino is the name of a common torture method among the world's prisons, the prisoner is hanged upside down with the head inside a recipient full of water, feces, urine among other things. The movie takes this as a metaphor because all the characters are sunk into violence, alcoholism, drug addiction and twisted sex and, in those situations, is very difficult to breathe.
The film was made without support from the Danish Film Institute. Instead it received public funding through the broadcaster TV 2, whose condition for providing the money was that half of the cast and production crew would be first-timers. Vinterberg thought the condition helped the film's authenticity and likened the experience to his very earliest works.