Metric Diving Australia uses the metric system. In this way, ten miles becomes something like 18 kilometers. That is why Australia is so large. If they used a normal system of measurements, Australia would be about the size of the Hawaiian islands. They also drive on the left side of the road, which is about what you would expect from an island full of English convicts. Of course, this is nothing new, as I have been there a few times now, but on this journey the metric system reared it's ugly head once more in an unexpected and evil way. A friend of mine, Alan, who lived in Australia (we met in Barcelona, Spain, obviously) recently decided to end his life, er, get married. He married a lovely mop named Peta, which in Australian sounds an awful lot like "Peter". When Alan first mentioned his new love, I began to think his last divorce was far, far worse than I had realized and began deciding how best to end the call quickly. Fortunately, he spelled out her name and gender for me, we remained friends, and booked my flight. Having been to Adelaide a few times, I decided to spend some time in Sydney before going to Adelaide for the wedding. After the wedding I would go in to Cairns (pronounced, inexplicably, as "cans") and the Great Barrier Reef. In the months prior to the trip I hurriedly got myself Scuba certified and cut my finger off. Once firmly ensconced in Sydney, I stomped around downtown and took in the sights, cooed my delight at all the native wildlife and repeatedly stepped in front of traffic. I also immediately sussed out the local dive shops and arranged for a dive Shelley Beach. Shelley beach is a ferry ride away from downtown Sydney, and is right next to Manly Beach (of course). In between Shelley and Manly is Baby Beach. On my first day of diving, our Dive Master began with a stern lecure titled: "If you touch this, you will die." The Australian East coast is home to a number of Deadly Things, it seems. There is the Blue-Ringed octopus, which if you touch, will kill you with one of the most toxic neurovenoms known to man. The toxin apparently leaves you fully concious and aware, but completely unable to move, speak or breath. Next is the Stonefish, the most venomous fish in the sea. Then there is the Lionfish, which is hardly worth mentioning here, as sometimes it is not even fatal. The lecture ended with the stern admonition: "Don't touch anything, but you'll probably still die." After suiting up, we trudged to the beach, waded in and swam out about 80 meters or so (metric, remember?) and began our dive. The other members of the group inserted their regulators, released the air from their vests and slid smoothly under the surface. Starting my very first "official" dive, I cooly released the air from my vest, promptly plummeted to sandy bottom and began looking for my regulator, all the while wondering how many stone, lion and blue-ringed Dangerous Things I had landed on. The dive master slowly drifted down, looked at me and made the sign of the cross (you can't communicate underwater except through hand-signs). After finding my regulator, verifying that I had not been stung to death and taken several breaths of sweet, sweet air I swam off to rejoin my dive buddies who seemed surprised to see me. The dive was simply incredible -- 15 meter visibility, warm water, and an incredibly diversity of colorful and vastly poisonous fish. We saw sea turtles, sharks and a motorcycle. It was like being Peter Pan, gliding effortlessly over the ocean floor, only not as gay. Throughout the dive, we all communicated with our dive master, through hand signals, to inform him of our air status. He seemed surprised to see me each time I reported my diminishing supply. A tank is normally filled to between 2500 - 3200 PSI. How long this lasts depends upon things like how deep you dive, how experienced you are, and how many poisonous fish have stung you. A new diver can go through air twice as fast as an experienced diver. Regardless of all these factors, however, the fact is you always have enough air to last for the rest of your life. In practice, we try to surface with 500 - 700 PSI in reserve. As my air supply dwindled to under 700 PSI, and we continued our dive, I begain signaling the dive master a bit more often. Each time, he gave me the "OK" sign. Each time he gave the sign, I assumed he meant we were almost there (back to the beach). At 250 PSI we were still swimming. Becasue I don't have a lot of experience, I have not established my air consumption rate yet, but falling back to my high-school math which I swore I would never use, I began to do some rapid air-consumption calculations. I started with 3000 PSI. We had been diving for 40 minutes. Thats 75 PSI per minute, but of course, that's an average -- the actual rate varies continuously with depth. So if f(x) = consumption at depth x, and my depth can be described as a function of time, d(t), then by taking the definite integral of f(d(t)) from 0 to 40 minutes... At 100 PSI I remembered that I don't remember my calculus well enough, and decided that 75 PSI per minute was an acceptable average. I now had an estimated ninety seconds of air left. I discreetly tapped the dive master on his tank and when he had slowly turned to face me, I signaled to him with one finger: "One hundred PSI". He nodded and gave me the "OK" sign. At 100 PSI, "OK" was not an answer I was prepared to deal with, and so I surfaced as slowly as my remaining air would let me. Back on the beach, I inquired of the dive master his reasoning for giving me the OK sign when I was at 100 PSI. He looked at me in some surprise and replied: "100 PSI? I though you had 100 BAR!". You see, in Australia, tank pressures are measured in bar, not PSI. But because I had brought my own equipment, my guage reported PSI. It turns out that 100 BAR is about 1500 PSI -- plenty of air to live.