With apologies to Garf but I was asked to tell this little tale.

I didn't want to put it in 'I learned about diving' because frankly I didn't!
On a cold new years day, many years ago I was preparing for the traditional dive in Torquay harbour. Bottles containing raffle tickets had been thrown into the murky harbour, each ticket representing a prize. With viz usually being a few centimetres, we tended to enter the water in pairs, then separate and search the harbour bottom solo by touch. Lovely.
So I found myself groping my way across the sea bed in 3 metres, completely unable to see. Then I experienced someting strange. I felt as though my fins were no longer pushing me forward. I kicked harder but nothing happened. I just couldn't understand it so I thought I should let the silt settle to see what was going on. As the murk gradually cleared I began to make out what looked like a grid in front of me. Looking up, left and right, it was all around me. What was this? Then it struck me. I had swum into an inverted shopping trolley through the hinged bit at the back.
Amazingly, despite the fact that this was the mid 80s and DIR was unheard of, I could backfin but try as I might, I didn't budge. My cylinder was wedged behind the 'gate' and I was stuck fast. Then something caught my eye. The last 50 bar of my SPG was marked in orange and there was a black line across it. I had 30 bar left! Jesus! I took stock of the situation. I can't move. I'm under the water. I'm running out of air. This is how I'll die. The panic started to rise in my chest. I remeber wondering whether I should just take my regulator out of my mouth because I didn't like the idea of it getting tighter and tighter. I'd rather have just got it over with.
But then it occured to me that I didn't want to die but I certainly didn't want to die looking like a plonker and I realised that I HAD to move. I knew what I needed was bouyancy and tried to reach my weightbelt to ditch it to give myself some lift without using air but I couldn't get my hand to the buckle. I could, however, reach my ABLJ direct feed and filled the old bog seat with air. And miraculously the trolley moved! But not far enough.
I strained and squirmed and amazingly found myself kneeling up on the harbour bottom. Still in the trolley but in with a chance. Without thinking too much about it I kicked off my fins, staggered to my feet and started walking. I knew there were some steps by the harbour wall and I had to find them. BANG! I walked straight into the harbour wall but where were the steps? Left or right? If I walked the wrong way I could well have walked to my death. I turned left. I don't know why. I had 10 bar left and the regulator started to tighten. Then the wall disappered. I had reached the steps cut in to the wall!
So up I went and emerged from the water with a shopping trolley wedged onto my upper body and my friends not able to belive what they were seeing! After a considerable struggle I was freed and never was a post dive pint more rapidly swallowed!