The wreckage of history

"You're dead," my computer announced. At least, that would be an apt translation of the frantic beeping that accompanied the "SOS, SOS" that flashed across its screen. It had come adrift from my wrist the day before and plunged straight to the bottom of 87ft of water and, if I'd gone with it and stayed overnight, I would indeed now have been dead. Fortunately, we'd dropped a marker buoy over the side and in the morning our dive guide had popped down to retrieve it. He'd reappeared 10 minutes later with my dive computer strapped to his wrist, still beeping furiously.

"You're dead," my computer announced. At least, that would be an apt translation of the frantic beeping that accompanied the "SOS, SOS" that flashed across its screen. It had come adrift from my wrist the day before and plunged straight to the bottom of 87ft of water and, if I'd gone with it and stayed overnight, I would indeed now have been dead. Fortunately, we'd dropped a marker buoy over the side and in the morning our dive guide had popped down to retrieve it. He'd reappeared 10 minutes later with my dive computer strapped to his wrist, still beeping furiously.

We were anchored in the Chuuk Lagoon, north of Papua New Guinea and east of the Philippines. Some people refer to it as Truk because the German colonisers (who came after the Spanish and before the Japanese and Americans) had trouble pronouncing Chuuk. Which explains why the island's best-named hotel remains the Truk Stop. Better known is the fact that the Chuuk Lagoon is the last resting-place of the 60-odd Japanese ships that were sunk during two devastating days of US carrier strikes in February 1944. Today, three "live-aboard" dive boats work what has accurately been described as a wreck-diver's heaven, and I'd joined the Thorfinn, a converted steam-powered whaling ship for a solid week of diving.

Lance Higgs, our sturdy Canadian captain, bought the Thorfinn in 1974 and, two years later, shifted her from the east Canadian coast to the west, via the Panama Canal. Somewhere in those southern waters he decided that life in the Tropics had a lot more appeal than working the frigid Canadian waters. He had the Thorfinn refitted in Vancouver as a charter cruising ship, a makeover which included such non-Arctic features as air-conditioning and a hot tub on the rear deck. Twenty-five years later, Lance is comfortably at home in Micronesia, running his ship with what is essentially his Chuukese wife's family as crew.

Diving Chuuk turned out to be much easier than expected. Many of the coral-encrusted wrecks were at easily reached depths, but some of the finest were deep, well below the 120 to 130ft commonly thought of as the sport-diving limit. There would be plenty of opportunity for "penetrations" (divers' jargon for going inside the wrecks) and, with up to five outings a day, enough dives to guarantee a nicely nitrogen-saturated bloodstream.

The water was clear, warm (never dropping below 80F), virtually current-free and blissfully calm. As a result, there was no need for thick wetsuits or the heavy weights that go with them, so the diving was relaxed, stress-free and, well, deep.

Three times during the week, I found myself below 160ft, comfortably deeper than I'd ever been before, but not the least bit concerned about my safety. Part of that confidence was certainly due to the unusually long "safety stops" we were instructed to take on the way up (the deeper you go and the longer you stay, the slower and more protracted your return to the surface should be).

Our group started out with 14 divers but 11 of them were victims of short American holidays and that left just three of us to enjoy the whole seven days. Pierre was a charming Frenchman, working for his bank's Hong Kong office, and Rhoda was an adventurous Englishwoman who'd left her husband behind in Tokyo to look after her two young daughters while she explored Second World War ships' engine rooms, 120ft below the water's surface, at night.

To get all that diving in, we set out after dark, torches in hand, to swim through the ships in the blackness. Straightforward though the diving turned out to be, none of us were beginners and all were well-equipped. Which explains why I headed down with that wonderful modern invention, the dive computer, strapped to my wrist. A large part of every diving course is spent studying "the tables", the columns of figures that tell you how long you can safely stay at any given depth - all of which is related to how recently you've been diving, and how deep and long that last dive was. Today, however, the state-of-the-art dive computer assesses how many minutes you've spent at every depth along the way and, as a result, how long before you should start coming back to the surface, how long you should take to get there, and, once you're back on the surface, how long you must wait before you can safely get on an aeroplane. That is if you manage not to lose the thing.

The one drawback with all this great technology is that everybody's computer had a different opinion. These essentially conservative instruments seem to have grown more so over the years. So, Pierre's brand-new Suunto computer was telling him, "don't fly anywhere until next week", while my two-year-old Aladin was saying, "don't fly anywhere until tomorrow", and Rhoda's ancient Beuchat was announcing that her flight was ready for boarding.

But what of the diving? It was fabulous. The 27 dives I made during the week covered 24 different wrecks, two of them aircraft (a Betty bomber and an Emily flying boat). After so much diving (or perhaps after just so much nitrogen in the blood) one wreck did tend to merge into another. But some really stood out.

The Heian Maru, for example. This converted ocean liner started just 30ft below the surface, with its name clearly visible on the bow. Its side stretched away like a coral-dotted football field and we made our way along what was once the top deck all the way to the stern, swimming round to inspect the huge twin propellers.

At another wreck, the Fujikawa Maru, we swam in through the bridge, inspected the officers' white-tiled Japanese bathtub, made our way down through the engine room and finally emerged into a cargo hold still packed with a jumble of fuselages and wings. At the bow, wartime suddenly morphed into fairyland - an exotic and colourful topography of corals and tropical fish turned this long-submerged wreck into a surrealist extravaganza.

Back to war, and in a rear hold of the Yamagiri Maru we saw shells intended for the battleship Yamamoto. The biggest British and German battleships of the war fired 15-inch shells, while the biggest American ships sported 16-inch guns. These monsters were intended for the 18-inch guns of the 63,000-ton Yamamoto and most were still neatly packaged in groups of four.

Then there was the Hoyo Maru, an oil tanker that was so intriguingly confusing we dived it twice. The ship had turned over completely as it sank, and the engine had broken away from its mounts and crashed down through the engine room, turning walkways and stairs into a chaotic jumble of bent and twisted metal. We swam in through the huge hole that was punched by the torpedo that had sent it down, then emerged to swim underneath the ship and pop up on its other side.

But the dive we all agreed that we'd do again, if we only had one more day, was the deep, deep San Francisco Maru. Dubbed the "million dollar wreck" for the sheer amount of arms and munitions that went to the bottom with this fully loaded cargo ship, she shimmered into view as we dropped below 120ft. There on the deck, just forward of the bridge, at around 160ft, we found three tanks. While down below in the cargo hold were trucks, their bodies rusted away but engines, chassis, wheels and tyres still intact. Wow.

There are direct flights to the island of Guam from Manila, Hong Kong, various Japanese cities (Chuuk is big in Japan) and Cairns. Once you get to Guam, it's just 1 hour 50 minutes to Weno, the main island in the Chuuk Lagoon. The adventurous can take Continental Micronesia's island-hopper service that goes Hawaii-Johnston-Majuro-Kwajalein-Kosrae-Pohnpei-Chuuk-Guam.

Three live-aboard dive boats operate on the Chuuk Lagoon: the 'Truk Aggressor' (www.pac-aggressor.com), the 'Truk Odyssey' (www. trukodyssey.com) and the 'Thorfinn' (www.thorfinn.net). The first two are modern, purpose-built dive boats, but all offer similar one-week, Sunday-to-Sunday packages including a berth in a shared cabin, all meals and as much diving as you could want for around £1,400. The three live-aboard dive boats that operate on the lagoon all have websites.

Chuuk is one of the four states that make up the Federated States of Micronesia (FSM) and, if you have time, it's worth visiting other FSM islands. Yap is particularly well-known for its strong culture and stone money, while Pohnpei has the wonderful Village Hotel and the spectacular ruins of Nan Madol.

Alternatively, once a year, the 'Thorfinn' makes two-week cruises from Chuuk to Yap and back to Chuuk again, stopping at a kaleidoscope of rarely visited atolls and islands along the way. Suitable for both divers and non-divers, these trips cost £2,700 per person, including all meals and, for divers, all dives