Alt-J frontman Joe Newman recalls in this song a childhood bedtime ritual where his mum would lull him to sleep by making ocean noises.
Many fans have interpreted the line "two tabs on your tongue" to be about acid, but that is not the case. Newman explained to NME that he, "imagined a pill that you could take that would dissolve a memory of someone."
The song ends with the lyric "knee-deep on the North Sea," which is a reference to jazz outfit Portico Quartet's Mercury Prize-nominated debut album. Newman explained to NME: "The title song ("Knee-Deep in the North Sea" ) is the best song of the noughties. They were such a huge influence."