"Octopus's Garden" is a song by The Beatles, written by Ringo Starr.
It's from their album Abbey Road (1969).
It's the second song he wrote for The Beatles, when he quit The Beatles in 1969. He quit the band and spent some time on a boating trip with his family, where he heard a story of how octopi travel the ocean looking for shiny things to keep.
Ringo Starr thought that this was amazing, how peaceful and happy it…
I'd like to be under the sea
In an octopus' garden in the shade
He'd let us in, knows where we've been
In his octopus' garden in the shade