I think that the song is about people living in the bottom half of the chakra system. IN THE TOWN WHERE I WAS BORN (the 1st base chakra(RED) is where most are born in civilized society(because of doctors and hospitals)). LIVED A MAN WHO SAILED THE SEA AND TOLD US OF HIS LIFE IN THE LAND OF SUBMARINES( a submarine is a chakra, and the man who sailed the sea is a man who knows of the chakra system). SO WE SAILED UP THE SUN TILL WE FOUND THE SEA OF GREEN AND WE LIVED BENEATH THE WAVES IN OUR YELLOW SUBMARINE (made are way up the spine through the 2nd chakra(ORANGE) and stopped at the 3rd chakra(YELLOW/SOLAR PLEXUS/SUN)right under the 4th chakra(GREEN/THE SEA OF GREEN)and go no further than the sea of green....never making it to the 4th chakra(GREEN/HEART) sea of green, sea of love, true love....AND OUR FRIENDS ARE ALL ON BOARD, MANY MORE OF THEM LIVE NEXT DOOR AND THE BAND BEGINS TO PLAY....WE ALL LIVE IN A YELLOW SUBMARINE, YELLOW SUBMARINE, YELLOW SUBMARINE....not everybody lives in a yellow submarine, they want you to live there, but you dont have to, its your choice...IM STILL GONNA LOVE YOU NO MATTER WHAT COLOR YOUR SUBMARINE IS!!!!