Mark I

On April 6, 7, and 22, 1966, The Beatles recorded a song for the Revolver album called Tomorrow Never Knows.  The working title was Mark I.  I was trying to find the significance of the working title and I believe I've found it. 

The British Royal Navy carried out operations near the end and after World War II "to clear the ports and harbours of the Mediterranean and Northern Europe of unexploded ordnance and booby traps laid by the Germans" according to the website:  http://www.mcdoa.org.uk/ (Minewarefare & Clearance Diving Officer's Association.)  The divers were called Port Clearance Parties or "P" Parties and wore Mark I and Mark II self-contained diving suits developed by the British company Siebe, Gorman and Co. (Check image on left:  the bottom suit on right.)

Again, I think the song reference is connected to Paul and the Lotus hyperbaric bed.

Photographer Richard Avedon took a photo of Paul in 1965 in a "spacesuit."

Very similar to the Mark I diving suit!!