The phrase "yellow submarine" refers to a song by The Beatles, where they imagine a magical submarine that's colored yellow. It's often used to talk about something exciting or imaginary. Full definition
It's not a leaky yellow submarine with krill - proof screen doors like Hard Working Realtor scuppers... I mean... skippers, but it is mine. (remonline.com)
We should sing «We all want a defensive midfielder» to the sound of Yellow Submarine on Saturday to wake Wenger up. (justarsenal.com)
United are set to follow up the appointment of Mourinho with the signing of Yellow Submarine defender Bailly, according to Di Marzio. (caughtoffside.com)