Have you ever noticed how some divers always see the good stuff?
     You know the type. You're on an expensive tropical holiday, describing how you just spent 15 minutes watching a nudibranch in a hole, and they look at you in disbelief and say: "Didn't you see the manta ray, then? Big or what? And tame! We all played with it - Glen was feeding it sugar lumps!"
     Yes, you know the type. They can do a solo dive in a sludge tank and come up smelling of roses and with a camera full of award-winning photographs. Bastards.
     Take my friend Otto von Effstoppen, as I call him. We'd done a few dives together with nothing spectacular happening, and I took all his tall tales with a pinch of salt. Then he bought an underwater camera. He invited me on a holiday to christen it, but as I'd already booked one, I declined.
     I should have known better. First time Otto used the camera: "It vos a baby vale shark! Yah! It vos only 8 metres long, so I could get zer whole fish in my picture! Here, look!"
     Now, I think I'm observant. I look around carefully. I look out into the blue, I look behind myself, up, down - I'm pretty determined not to miss anything.
     But I still do. I remember one weekend on a club dive when everyone saw a seal - except me. It looked them over, nibbled their fins, balanced a ball on its nose.
     As soon as I heard, I was back in the water in a flash. I swam around looking everywhere for that seal, barking into my regulator like a demented dog, clapping my hands, jumping through hoops, but I needn't have bothered. I had as much chance of seeing a mermaid.
     I started to get paranoid. Did I smell? Had I peed once too often in my wetsuit? Inspired by Otto, I bought a camera too. But it just seemed to make matters worse. The minute my camera gets wet, natural laws of chance and probability fly out of the window.
     My photographic mentor, Angus McBoyle, soon let me in on McBoyle's Laws of Underwater Photography.
     The First Law states that: "The size of the intended subject is inversely proportional to the size of the actual subject." In other words, if you have a close-up lens on, you can bet that all the nudibranchs have gone into hibernation, while a smorgasbord of sharks, whales and dolphins will pass by as if queuing for Noah's Ark.
     Which brings me to McBoyle's Second Law: "You'll always be looking in the wrong direction."
     Every time it happens to me, I have nightmares. I'm hanging beneath the boat doing a safety stop, eyes fixed on my dive computer, oblivious to the fact that, behind me, a huge albino sperm whale is flossing its teeth on the anchor line.
     I wake in a cold sweat, staring at my watch, then lapse back into a fitful sleep.
     Again I'm beneath the boat, but this time I turn and see the whale. Selflessly, I start screaming and banging on my tank so that none of the others will miss it.
     From out of the blue, a posse of divers with flashguns blazing descends on the scene. I finally turn to take a picture - only to catch a glimpse of tail flukes disappearing into the blue. To rub my nose in it, I notice that the frayed anchor line is festooned with shreds of huge, half-digested calamari rings - and green stuff that looks suspiciously like spinach.
     This can go on for days. It's McBoyle's Third Law: "If you do see it, you'll forget about the camera."
     With all this going on, you may wonder why I don't just give up, forget about the camera, flog it. Now that would be stupid, because that's when McBoyle's Fourth Law of Underwater Photography kicks in: "The day you leave your camera behind, you'll really, really regret it."
     As McBoyle, resplendent in red tartan wetsuit and neoprene sporran, once explained to me: "That's the day you'll see everything, laddie. You'll see swordfish fencing, a shoal of tuna being over-friendly to a dolphin and dogfish chasing catfish into coral trees.
     "John Dories will be telling tall tales of cure-aIls for fin-rot and trench-gill. Coelacanths will dance on their fleshy fins to the sound of Otis Herring, the Four Topes and Diana Wrasse. Your eyes will pop, your jaw will drop and you'll grope in vain for the camera that isn't there!"
     So how do you cope? First, you tell yourself it's all down to luck and realise that, until PADI brings out a Lucky Diver speciality course, you're stuffed.
     Then you discover that there are others even less lucky than yourself - like my friend Gareth, who flooded his camera on its very first dive.
     Finally, you convince yourself that having two or three cameras will push the odds in your favour.
     You see, it's addictive, this underwater photography. No matter how crappy your photos, you are sure that more kit, more money and more time will fix it.
     So until someone starts up Nikonos Anonymous, I'm going for broke. And if you have any spare cameras you don't need any more - contributions will always be gratefully received!