Double Chemistry
As we are all well aware, oxygen atoms wear sky-blue T-shirts and have two arms, while nitrogen atoms wear olive-green T-shirts and have three arms. Graham Sands, meanwhile, has an important decision to make...

Confusing, isnt it, that the hand signal for Shark! is almost identical to the one for Sorry, Ive got a splitting headache.
Subtle difference in the thumb placement, thats all. I am so astonished by my partners signal that I swing round in a hurry, and my kit smashes through a buddleia bush. Thank goodness this isnt the International Year of the Leaf.
Were still in the driveway, loading the car for the trip. We have a big day ahead: this is to be my partners first dive in British waters. So whats with her sudden anxious signal Has she spotted a leaf shark
Ive forgotten it again, she confesses. That bit about oxygen and nitrogen. Which is the one I need to breathe out when we come up
Her anxiety enfolds her like an atmosphere, 21 per cent concern for her own safety and 79 per cent fear of screwing up and harming her buddy. My feelings are similar, but half the point of being the lead diver (and the entire point of being the man) is not to show it.
So as we head off down the motorway, I go through the theory lecture again. Oxygen atoms wear sky-blue T-shirts and have two arms, while nitrogen atoms wear olive-green T-shirts and have three arms. Down into the lungs they troop, two by two in colour-coordinated pairs, where they find big red buses with plenty of seats for the oxygens, but the nitrogens arent allowed on.
Some of the nitrogens get fed up and start walking into the bloodstream, and as the crowd pressure builds up, more and more of them take this route
OK, so you try explaining respiratory physiology to an arts graduate, who can quote you all the shipwreck scenes in Shakespeare, but has no idea which gas mixture they descended on.
If only she had gone to a northern grammar school like mine, with its verruca-laden swimming pool, and double chemistry on Tuesday afternoons, and learned to dive in cold brown waters.
Picture her drifting along in a jack-knifed position, arms reaching down like jellyfish tentacles, the left making delicate little paddling motions, the right gripped by me as I tow her across a coral garden at 3m. Her bum breaks the surface like a bifurcated SMB and its accumulating sunburn adds a new dimension to my calculation of bottom time.
Advanced diving this wasnt, but good experience for a diver of my level. Almost as good as the time I went to the Lebanon and they offered me an inflatable woman, which I assumed I was meant to take diving.
The point is, my L-shaped partner represents the shape of the future: unmuscled, unmoustached, and benignly bent as a wall bracket. Think of all the tourists who train and enjoy diving in tropical waters, and how few of them try it in Britain, unless they happen to have a buddy plugged into the British diving scene.
A few years ago, when the BSAC introduced its Ocean Diver entry grade, we were told to expect a big increase in the number of people looking to try diving here. Would your average club be ready to welcome and retain them, we wondered, or would they go off and do their own thing at Swanage or Stoney Cove, with 20 dives experience between the whole Volvo-load of them, and a boot full of unfamiliar kit, after talking to some guy in the pub who said it was easy-peasy
But conversion courses were only part of the story - incomers needed to be offered positive reasons to dive here. Put it this way: my first wreck was a brilliant, coral-encrusted battleship, and it made me glad I had taken up diving. It would be depressing if my partners first wreck was the shell of a Datsun Cherry, inhabited by a solitary stickleback.
We are off the motorway now, and the roads narrow as we approach our destination. Houses and fields press in on either side, while up ahead a bank of cumulo-nimbus masses. My partner frets: it doesnt look good, lets come back another day.
Look, you want Caribbean blue, go buy the Enya album. This is a good day for diving in Britain. To calm her jitters I remind her of Brendan, who we met on our last trip. He had had the same training as my partner and logged the same number of dives, but all in a cold, dark hole near Blackburn in February. Nothing in his experience could have prepared him for the warm, clear waters of Mexico, yet he had no trouble adapting.
Easy-peasy, I tell her. She peers dubiously out of the windscreen at the dwindling sliver of light blue sky ahead, as an oxygen atom might peer out from the top deck of a bus at streets suddenly full of olive-green T-shirts.
Nearly there. Shallow holiday dives are all very well, but we have no other diving experience in common. We are like creatures apart, like oxygens and nitrogens that consort but do not combine. Can today bring us together in a double chemistry
A lot is riding on this - a bad experience and she will be unlikely to try again. So the site must be safe, sheltered and accessible. More than that, it has to show her what diving in Britain is all about.
So I looked long and hard before picking todays spot. I wrestled with kelp and contemplated congers. I counted deadmens fingers on lost merchant shipping. I gazed over skerried sea lochs on the far side of Oban, where the vista seemed to merge into the collective dreaming of seals, like the Hebridean Overture re-written in notes of late afternoon sunshine.
But always the inner voice warned: not yet. This is a fine place, but not for my Piscean partners first try. Theres one place it just has to be.
Yup. Right here.
Stuff the seals. Forget the congers. What we have here is a rubble-and-puddle car park, a collection of sheds and a view of flat, damp fields on the outskirts of Peterborough. And as for that reed-fringed square of water - its too small to call it a lake, you would have to say its a jolly big pond.
But its perfect for our purposes, and for 40 glorious minutes at 8m, we enjoy warm sunlit water and bright perch, and the finale is a magnificent pike.
Glorious Gildenburgh, and my partner gets her first British dive in her logbook.

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