Two tracks were remaining on the tape, and The Beatles raided the trap room at Abbey Road to find suitable instruments and effects. Onto the first the following sounds were added, in rough order of appearance:
- John Lennon blowing bubbles into water using a straw
- George Harrison swirling water in a metal bathtub
- Two ships' bells being rung
- A noisemaker being rattled
- Low-level voices for a party atmosphere
- An ocarina, played by The Rolling Stones' Brian Jones (heard during the third verse)
- A propeller being wound and put into water
- Coins being scattered
- A foghorn
- The final singalong
The fourth track contained similar effects, again in the order in which they appear:
- Chains being rattled in the bathtub
- Clinking glasses
- More party chatter
- A brass band
- Lennon, recorded in the studio echo chamber, shouting naval phrases into a microphone connected to his Vox guitar amplifier
- Whooshing sound effects
- Lennon's "life of ease" vocals
- A marching band drum played by Mal Evans
The brass band was made up of session musicians booked especially for the session, although their names remain unknown. The final chorus, meanwhile, was sung by anyone on hand in the studio, including Mal Evans, Neil Aspinall, George Martin, Geoff Emerick, Pattie Harrison, Brian Jones, Marianne Faithfull and The Beatles' chauffeur Alf Bicknell.
Ringo Starr also recorded an unused introduction, a brief spoken word passage accompanied in part by the other Beatles:
...yellow submarine. And we will march till three the day to see them gathered there. From Land O'Groats to John O'Green, with Stepney do we tread. To see us yellow submarine. We love it.
The words were in reference to Land's End and John O'Groats, the southernmost and northernmost parts of the United Kingdom. Underneath the vocals was the sound of a box of coal being shaken, in an approximation of marching feet.