Short answers, pulled from the story.
Octopus's Garden was written and sung by Ringo Starr, credited under his real name Richard Starkey. It was only the second song Starr had written, and George Harrison provided uncredited assistance with the chord changes.
Starr came up with the idea in 1968 while on a boat belonging to comedian Peter Sellers in Sardinia. The boat's captain told him that octopuses travel along the sea bed collecting stones and shiny objects to build gardens. Starr was also inspired by a desire to escape the growing tension among the Beatles.
Octopus's Garden appears on the Beatles' 1969 album Abbey Road. It was the last Beatles song released with Ringo Starr on lead vocals.
The Beatles recorded thirty-two takes of the basic instrumental track before they were satisfied. The session took place on the 26th of April 1969, with George Martin absent and his apprentice Chris Thomas present in the control room.
The bubbling sound was created by George Harrison blowing through a straw into a glass of milk, at Ringo Starr's request. It was added to the recording as a studio effect.
Oasis and Noel Gallagher used lyrics from Octopus's Garden on multiple occasions. The phrase "I'd like to be under the sea" appears in the refrain of their B-side Take Me Away, the chorus refrain can be heard near the end of The Masterplan, and the band frequently used the same refrain to close live performances of their 1994 single Whatever.