I am a big-city boy who gets uneasy when the water pressure in the shower gets too high. Nevertheless, I promised myself long ago that someday I would learn to scuba dive. Unfortunately, someday is here, in Australia, with the Great Barrier Reef beckoning.

My inquiries unearth a number of instructors, all of whom emphasize how safe scuba diving is. Translation: There's a good chance I will be killed. When's the last time you heard a teacher say, "Look, I swear: Ping-pong is safe!" In fact, I suspect there is an inverse relation between how dangerous a sport is and how safe its instructors assure you it is: "Hang-gliding? One of the safest sports ever invented," or, "Golf? Hey, those balls can kill a person."

But because my soul yearns for adventure, and because I imagine how ashamed Lloyd Bridges would be of me if I wimp out, I decide to take the plunge.

I call up various schools and talk to as many people as I can. With any luck, by the time I decide on a class, it will be time to go home. I read, I sort, I sift, I eliminate, I talk, I compare. Finally, I throw all the pamphlets up in the air, stab one with a pencil and enroll.

My instructor is Rick, who looks like Jerry Lewis in the Marine Corps and speaks like he's already swallowed too much saltwater.

The first morning, I sit in the classroom while Rick introduces the equipment and the fail-safe procedures that make scuba diving so safe. By the end of the morning, I've counted 27 new ways to die. After all the theory is over, it boils down to one thing: "Breathe or drown."

Rick emphasizes that one of the most important things to learn before diving is the signals that alert your "buddy" you are in mortal danger. He illustrates by making a rapid chopping motion under his neck, which means "I'm out of air." To be on the safe side, my buddy and I devise additional signs: Flapping our arms hysterically means "I just remembered I can't swim," and kicking our legs vigorously while swimming upside down signals "My head is stuck inside a giant clam."

I hear Rick say that 90 percent of people who die scuba diving do so because they get scared underwater and yell "Help," forgetting that you can't yell "help" -- or anything else -- down there. Suddenly the person beside me jolts me with a sharp elbow. Rick hasn't said that at all; I've fallen asleep in the classroom. Where's the action?

Despite all that instruction, my first time underwater is a disaster. I suck frantically for air and become so disoriented that I fear I'm hopelessly lost at sea. This is very embarrassing, since we're still in the swimming pool. I begin to wonder if I should stick to checkers. Rick tries to convince me that it's advantageous to learn in a cloudy pool, where I can't see in front of my nose, because it's probably the worst conditions I'll ever encounter. But I know the owner is just too cheap to clean the pool.

Finally the classes are over, and it's time to take the test to see if I qualify to be a certified scuba diver.

I descend to the ocean floor with Rick, and he instructs me to take off my mask and put it back on again. This is the part I have been dreading all week, because once I remove my mask I a) can't breathe, and b) can't see. Rick takes my mask from me, and in the few seconds before he hands it back (which seems like hours), it occurs to me that Rick could kill me now if he wants to, and it would be the perfect crime. I realize, of course, that he has no motive, but I come from New York City, where, of course, he doesn't need one.

Rick informs me that I've passed the test. Actually, everyone in our class has passed the test, including the kid who kept doing "Flipper" impersonations. This worries me. I'm now certified and can go diving without an instructor, but somehow I don't feel like a certified diver.

But the time has come for my first dive. I put on my buoyancy control device -- an inflatable jacket that enables most divers, by pumping air into and out of it, to swim at one depth. Not me. I'm going up and down faster than a yo-yo.

Eventually I get it figured out, relatively, and start exploring.

I'm amazed at how much there is to see once I get below the surface, even though I feel like a fish out of water. There's something oddly familiar about being weightless ... Of course, it feels just like the night before payday!

There are fish everywhere. Big fish, little fish. I vow to learn their names. Telling my friends I saw big fish and little fish will not impress them much.

I can almost touch them, yet the fish act like I'm hardly here. Imagine how freaked-out people would be if giant fish wearing masks suddenly appeared and tried to touch them. Humans would no doubt harpoon first and ask questions later.

Suddenly, I see a shark.

I recognize it as a reef shark, one that supposedly isn't interested in humans. I pray it isn't near-sighted or brain-damaged, and recognizes me as such. I breathe a large sigh of relief when it swims away.

Then I look at my gauge and notice that my air supply is almost gone. That large sigh used up quite a bit! I ascend with my buddy, and board the boat. I'm alive!

Now it's time to return to New York. Unfortunately, everyone I meet makes the same remark: "Scuba diving? That's easy. New York? Now that's dangerous."

Stan Sinberg is a New York writer.