Face to face, what can be expected of such a meeting?
Facing death or the adventure of a lifetime?
Sometimes only a four lettered word will do, and this is one of them. I mutter it silently to myself as nature's number one predator appears from the abyss. More expletives follow, slowly at first and then rapid fire as the full might of the ocean's greatest hunter turns and heads straight towards me. Closer and closer, with a mouth opening and closing as if in anticipation, it is Carcharodon Carcharias otherwise known as the great white shark.
The only thing separating me from those infamous teeth, now only 12 inches away from my face, is the mesh of a stainless steel cage, and I can't help noticing that some of the bars are bent. How did they get that way? Are they strong enough to withhold this cartilaginous hulk's curiosity? If you could see my eyes they would be out on stalks, my eyebrows on full extension by the sight transfixing me. But it is awe induced not by terror, but by wonder.
"People expect to find a mindless eating machine that attacks everything and everyone," says Morné Hardenberg, our shark diving guide. "But they go away with a different perception."
The great white is an incredible creature. Over 400 million years it has evolved into the ocean's largest predator, a torpedo shaped hunting machine equipped with sensors that can pick up the electro-magnetic pulses every living thing beneath the sea produces.
Its colouring is ideal for the hunter. It's surely no accident that it has been copied by military aircraft; the light underbelly to blend with the surface, the darker steel blue top side that makes it hard to spot from above, and broken lines of contrast to complete the camouflage.
What could be more exciting than coming face to face with it? Never mind that you're more likely to die from falling down the stairs than from a shark, it's the imagined fear that's exciting. Just hum the theme from Jaws and imagine that dead eye stalking you in cold dark waters.
Since it started about ten years ago cage diving has become more and more popular. Those to have enjoyed the experience include Prince Harry on his recent tour of Africa, who saw a shark maul a seal, and Brad Pitt.
But not everyone is enthusiastic. Many locals accuse diving operators of encouraging sharks to enter waters where humans swim by the practice of 'chumming' - where fish is thrown to attract them.
Although attacks are rare, about four a year for the whole of South Africa, they do happen. A few weeks before my arrival a British surfer nearly lost his leg to a shark in Cape Town and last year an elderly swimmer lost her life to a shark in the same bay. But diving operators say chumming only attracts sharks that are already in the area.
"Chumming has got nothing to do with it," says Michael Rutzen, owner of Shark Diving Unlimited. "We chum with animals that occur naturally. Chum where there are no sharks and you don't get any." It's a view supported by shark environmentalists.
Rutzen adds that shark diving has a vital role to play in re-educating the public and protecting the great white. "We have to show people these animals to ensure their survival. It's no different from viewing leopards and lions."
Cage diving occurs off Gansbaai, about 120 miles east of Cape Town, South Africa.
We set off in a 42ft double decked boat to 'shark alley' a narrow channel between two islands about a mile offshore, one of which is home to a colony of 50,000 seals. It's a feeding ground for hundreds of migrating great whites, some of whom end up in Australian waters.
After dropping anchor the process of 'chumming' begins. Parts of tuna, soup fin shark and other fish are tossed overboard.
Suddenly the excitement on board is palpable - the first shark has been spotted and it's circling the boat. The cage is lowered and tied on securely at four points. I step into it and the waterline reaches my neck. It is large enough for five of us. The water is cold. As the skipper and crew spot sharks approaching they shout the command, "Down. Down. Down." We hold our breaths and go under. The cage doesn't move - it remains wedded to the boat.
My first thought on seeing a great white is how graceful and powerful it is. One swims past our cage and I and the others can't resist touching its rubbery skin. We surface to a strict telling off. "No touching," shouts skipper Frank Rutzen. "They are not puppy dogs."
I don't need any reminding with the second shark. It heads right for me, bashes the cage and starts chomping on the bars, just inches away.
Scared? Too right I am - I can't hug the back of the cage hard enough. But it's exhilarating and I surface to cheers from the boat.