 Aqualung is the fourth studio album by the rock band Jethro Tull . Released in 1971 , Aqualung , despite the band 's disagreement , is regarded as a concept album featuring a central theme of " the distinction between religion and God " . The album 's " dour musings on faith and religion " have marked it as " one of the most cerebral albums ever to reach millions of rock listeners " . Aqualung 's success marked a turning point in the band 's career , who went on to become a major radio and touring act . 
