Yellow Submarine is credited to Lennon and McCartney and released as a single in 1966 as a double A-side with Eleanor Rigby. It has been given psychedelic overtones by the subsequent 1968 film. However, Paul McCartney has said that he wrote it as a children's song and denied that it had any associations with drugs.
It was written as a light song as shown by the fact that Ringo is on lead vocals. He often sang on the Beatles lighter songs such as "Octopus's Garden" and their cover of "Act Naturally". As with most Beatles singles, it was a huge hit going to number 1 in the UK and #2 in the US.