Asia Pacific With Quicksilver, an in-depth Great Barrier Reef tour By Shane Nelson / October 25, 2011 Share 1 -- Forty-five miles due east of Australia's Cape Tribulation, I was awash in the Coral Sea's mounting crush and having second thoughts about touching a giant clam. Only minutes earlier, I'd watched a snorkeling marine biologist from Quicksilver Cruises point out an open clam the size of a monster-truck tire. Before diving down to brush it gently with her fingers, she explained to a small group of us how Hollywood had helped falsely brand the sea creatures as man-eaters. A grudging, unhurried jerk followed, and the clam gradually closed its dazzling maw, concealing most of its velvety, electric-blue flesh within the corrugated confines of a far drabber shell. The process looked simple enough, and shortly after the guided tour finished, I located a giant clam of my own and decided to get a closer look. Sucking in a series of hurried breaths -- hyperventilating apparently helps one go longer without taking a breath -- I bit down on my snorkel and plunged headlong into a canyon of pastels. An undulating patchwork of muted colors from the surface, the reef became increasingly tangled and complex as I pulled myself closer, descending on the fragile metropolis of coral. Finally just a few inches from the biggest clam I'd ever seen and struggling some with that depth's pressure, I reached out to see what the shell of a wrongly accused man-eater felt like. I ended up stopping short, though, captivated by the colors. It looked like the clam had swallowed a gleaming swatch of green and blue leopard print, and I didn't want anything to do with closing up all that brilliance. Far-out splendorClients who join one of Quicksilver's outer Great Barrier Reef excursions are in for quite a journey. The sailings depart from Port Douglas in northern Queensland and travel just over 45 miles to the edge of Australia's continental shelf and the marine preserve at Agincourt Reef. The trip takes about 90 minutes one way. Talk with Doug Baird, a longtime marine biologist for Quicksilver and the company's environment and compliance manager, and he'll tell you the long voyage is well worth the time. "If you visit an inshore reef, that may not have a great diversity of coral, and it may not have a tremendous amount of fish life, mainly because of its proximity to the mainland," he explained. "Whereas going with us out to the edge of the continental shelf, we can bank on [150-foot-plus] visibility just about all year round, and there's a tremendous diversity of corals and fish." Covering a total area of more than 134,000 square miles, the Great Barrier Reef is roughly the same size as New Mexico, and perhaps not surprisingly, many of its most pristine regions are those farthest from where people live. During our interview, Baird mentioned a range of factors that can be harmful to corals, including sediment runoff, water temperature, salinity fluctuations as well as a growing concern linked to global warming: ocean acidification. "The more carbon dioxide the oceans absorb, the more acidic the ocean is going to get," he said. "Corals rely on being able to remove calcium carbonate from the surrounding water then lay that down as a skeleton. Calcium carbonate skeletons don't tend to live well in acidic conditions." Despite those concerns, the Agincourt Reef preserve certainly appeared healthy during my recent visit, and the assortment of both corals and fish was phenomenal. "It is a full day," said Alana Pietrzak, a Los Angeles-based marketing manager for Qantas Vacations, of Quicksilver's outer reef excursions. "But you get to fully experience the colors of the reef, and there's a far better chance to see all kinds of marine life out there." Finding NemoPatient snorkeling isn't a strong suit of mine, and I'm frequently guilty of trying to see too much as soon as I get my fins wet. According to Baird, narrowing one's focus often yields better results. "What I find most interesting -- and what I try to get folks to do, as well -- is just to follow a fish and see what it does," he said. "See how that fish interacts. See what kind of distance it covers. See what it's feeding on. ... Some fish will spend their entire life cycle in an area not much bigger than a coffee table. Clown fish, for example, tend to spend almost their entire life on one anemone." Baird told me that actually spotting a clown fish, however, can be tough even for the most patient observers. "On the movie screen, Nemo looked 4 feet long," he said. "In reality, Nemo is about an inch or 2 inches long. ... And they're also pretty shy. When something creates a big, dark silhouette above them, most of the shy and retiring fish tend to take refuge." Snorkeling is, of course, only one of many options folks can enjoy once they arrive at Quicksilver's expansive outer reef platform. Those not interested in swimming can join a tour of the region's coral formations on the company's semisubmersible vessel or simply look out the anchored platform's underwater viewing observatory at all kinds of fish -- or passing loved ones. For an additional fee, patrons can take introductory scuba lessons or plan a certified dive, and Quicksilver also offers novices a helmet diving experience where participants walk along a reef platform in a viewing contraption made mostly of glass. And there's the premium helicopter adventure taking off from a nearby platform, enabling guests to admire the Great Barrier Reef's staggering scale and mesmerizing formations from high above. "Being Australian, I'm always amazed when I go out to the reef," said Pietrzak, a native of Cairns, Australia, who told me she's gone on at least five Quicksilver cruises. "There's always something magical about being out there, and I learn something new every time I go." Commissionable to agents, Quicksilver's seven-hour outer reef cruises cost $210 for adults and $107 for children and include a light breakfast and buffet lunch. The company also offers a $534 rate for families of two adults and two children. Visit www.quicksilver-cruises.com.