I'm already feeling sick to my stomach when I arrive at the gates of Sea World. Of all the "adrenalin-themed" activities I had scheduled for my trip - skydiving, jetboating, abseiling down cliffs - the chance to swim with sharks was the most alarming, by some distance.
Not that anybody seems to care. "Unfortunately I have to advise that the Sponge Bob Square Pants show at 2.30pm has been cancelled because of the rain," the attendant at the gate says, as she hands over my ticket.
Circled on my map is the theme park's Mordor. On the way I almost forget my troubles as I pass a log-flume, delighted toddlers clutching balloons and waiting for their photo with Dora the Explorer.
Then I arrive at the Shark Lagoon. My advice is not to be early - with 10 minutes to spare, I have time to walk around the perimeter and be struck by a "what the f*** am I doing?" moment.
The waters below seem to boil with the dark outlines of huge rays, exotic fish, and a large number of, frankly, massive sharks (I had hoped there would just be the smaller reef sharks).
A slightly homesick Nick Anson, who is originally from Orewa and has worked as a diver at Sea World for almost eight years, gives me the run-down. The Shark Encounter runs only on the three days of the week the sharks are fed. Members of the public join a staff member as they feed the sharks from within a clear acrylic cage.
The enclosure is home to seven sharks, including the "boss" Elle, a bull whaler shark, and Dorothy, a 3.5 metre dusky whaler shark.
After the appropriate waiver forms are signed, I'm put in a wetsuit and snorkel and taken out on a boat to the corner of the enclosure where the feeding tank lies. Just big enough to fit two people side by side, and about 3 metres tall, it tips forward as I gingerly step on to its ladder.
As soon as I have my head under I look up and almost straight into the emotionless eyeball of a three metre shark (I'm later told he's a young male bronze whaler called Bullet), who has cruised silently up to the tank to check out the new arrival.
But apart from that unnerving introduction, my dread is soon replaced by a sense of wonder. As a small window is opened and a squid put out on the feeding stick, dozens of fish swarm to it, and through the glass floor of the tank a carpet of tennis racket rays and giant shovelnose rays (often mistaken for sharks) covers the enclosures bottom. Nearby, a school of fish swim around and around in a flashing silver circle, protecting their weaker members.
The sharks, on the other hand, don't swarm. There is no butting of the tank, no open jaws at the glass. When they come they circle in slowly, gliding and graceful. Dorothy, the largest dusky whaler and mum to many of the other sharks, is the most interested. When she takes the squid from the stick it is careful and deliberate, not ravenous or wild. We in the tank are utterly ignored - just spectators with the most remarkable of vantage points.
When I blow water from my snorkel after ducking down for a better look I am conscious of it. I try to be as still as possible - not out of fear, but so that the sharks are more likely to come in close. At one stage, Dorothy swims quickly away from the bait after being spooked by an equally-hungry stars-and-stripes puffer fish. Nick explains the Sea World divers swim freely in the enclosure (in chain mail for insurance purposes) every day without incident. The sharks get used to them, but when a new diver starts work Elle will circle in as if to say, "I'm the boss here".
When my time is up it's hard to leave - I feel like I could have stayed in for hours. As we hop off the boat a baffled grandmother bails Nick up, demanding an explanation. "How can you be in there with the sharks?" she questions. "Are they a different type? Why don't they attack you?"
"People come with their preconceptions," he later tells me. "They expect them [the sharks] to be biting the cage. But they're taken by how graceful they are."
The Shark Encounter programme is available for guests 14 years of age and over for $188 per person.
Limited Shark Encounter programmes are available on Monday, Wednesday and Saturday and have two participants per programme.