The massive flight deck is at 42m.

If I were to say Id dived the Big O, Id be misleading you.

I made four dives on it shortly after it was sunk 25 miles off the coast of Pensacola on Floridas Gulf Coast. Thats all.

It took a couple of noisy hours to get to where the wreck lay. It was noisy not only because the diesel engine of the aluminium Newton boat howled all the way there, but also because the dozen or so passengers continually shouted loudly and excitedly to one another in anticipation.

Once there, Richard, one of the good-ol-boy dive guides, swam down to the top of the wreck and tied a line to it, deploying at the same time a horizontal travel line to near the stern of the boat, itself tied to a lazy shot hanging at 6m.

This gave us an unmistakable route to where we needed to go. It was essential. A heavy layer of what the boys called whale-snot clouded the shallower water and the occasional stinging cells added a bit of spice to the quick swim down through it.

The Big O is the USS Oriskany CVA34 - a decommissioned aircraft-carrier of Korean and Vietnam War vintage that proved too expensive to get up to scratch as a floating museum of naval air warfare. Recession in the ship-scrapping business meant that it could be sunk as the worlds largest artificial reef instead.

Why Pensacola Its the birthplace of US naval aviation. Personnel from US and other allied air forces travel here to learn the niceties of high-performance flying, and Pensacola is home to the Blue Angels, the US Navys crack aerobatic team. Read that as Top Gun.

We were the unsuspected audience for a dramatic display of synchronised flying by four Blue Angels during our second boat ride out. At the same time, another couple of jets did vertical climbs and near-suicidal head-on low-level passes while inverted.

It was all very exciting Boys Own stuff. Most of our fellow- divers had some sort of connection with the military fliers, whether US or European.

The USS Oriskany saw more sorties flown than from any other aircraft-carrier during the Vietnam War. Steeped in military history, it seemed appropriate to sink it here.

Why do I say it would be misleading to claim I had dived it

Because at around 900ft long, and lying upright on a seabed that is 65m deep, an all-round tour is quite a daunting prospect. I reckon it would take at least a week of diving, not the four quick dives I managed.

Everything about the Big O is, well, big. The upper parts of its superstructure, or island, form the shallowest part of the wreck. It stands 46m tall from the seabed. Its flight deck is 42m deep.

Oriskany (put stress on the risk when you pronounce it) is a massive, awe-inspiring vessel, even in its watery grave.

During the sinking on 17 May, Oriskany turned and tipped before disappearing from the view of observers at the surface. It had been only 37 minutes since destructive detonations had provided the coup de grace.

Among the first divers to visit the wreck was local man Travis Allinson. He told me he was amazed to find that Oriskany had settled on the seabed perfectly upright, but thats how it lies, still looking as if its steaming ahead.

Travis looked after us during our visit to Pensacola. He took on the role of chief dive-guide for MBT Divers, the technical dive shop that had invited us over to see the new wreck.

This full trimix and nitrox facility is run by Jim Phillips and Fritz Sharar.

Hurricane Ivan made landfall at Pensacola and, at the time of writing, rebuilding is still in progress. Part of the movie Jaws was shot here, too, so its no surprise that the beach looks like Amity Islands, though we never saw a police chief who looked like Roy Scheider!

Pensacola may be in Florida, but its not tourist America. Its the real thing. Travis is a typically tobacco-chewing, baseball-cap-wearing, pick-up-truck-driving all-American guy.

We christened his truck, a little bigger than anything we are used to in the UK with its 5.9 litre diesel engine, the Queen Mary. Each day he transported us the 10 miles from the dive shop to the marina, where the newly acquired Newton dive boat was loaded.

The dive-boat is run independently from the dive shop and captained by Doug. He acquired it in anticipation of the extra demand for dive trips that the Big O would bring, and in consideration of the distance the wreck lies from shore.

My initial feeling, as I followed the line down through the murk, was that, wetsuit apart, this was a very British-style diving experience.

Yet as I reached 22m, the visibility magically cleared, and there was the ship, glowing a ghostly shade of pale in its coat of tropical light grey paint. It is extraordinary that the wreck is already smothered in schooling bait-fish. These in turn attract the amberjacks and bonito that prey on them, and all this after having been sunk for little more than a fortnight.

The prospect for the wreck attracting a lot of marine life is good. The metal-work already houses hundreds of tiny crabs.

Named after a famous battle in the American War of Independence in 1777, Oriskany was a modern carrier vessel. Unlike, say, the USS Saratoga at Bikini Atoll, she carried no big guns, nor was her control tower armoured.

Her aircraft were her armaments, and their range meant that the vessel could be kept as a floating airfield, well out of harms way, with other escort ships doing picket duty to protect her.

Initially deployed in the Mediterranean in 1951, the Oriskany was later the first vessel of her type to pass round Cape Horn. She was continually updated, and one of the first carriers to sport an electric escalator to get flight crews to the upper decks quickly and easily.

In 1961, she became the first aircraft-carrier to be fitted with the revolutionary Naval Tactical Data System (NTDS).

The deck is as big as an airfield - it would be, wouldnt it One deck down is the aircraft hangar, a massive void in which it would be easy to get lost.

Various parts of the vessel are decorated with the complex motifs, painted by past crew-members, that distinguish US warships from those of other nations.

Lovers of brass will be disappointed. This is a modern vessel filled with electronics and masses of wiring. Parts of the aircraft elevators were removed before the sinking.

Procedures for diving this fresh wreck were still being evolved. Most of the passenger divers were typical holiday-divers who wanted to be able to say they had touched the deck - just about achievable with a single tank of nitrox 28. You dont need to be a technical diver to see the superstructure.

We were hoping to go a bit deeper and stay a bit longer, but the requirement to ascend the anchorline was compounded by a current ripping across the deck.

This meant that a swim any way out of the shelter afforded by the super-structure would mean an ascent up

our own SMB line, and a drifting decompression schedule. There would be no way of making it back to the line. At this time. Doug wasnt ready to pick up drifting divers, and one German trimix rebreather diver who did this caused a bit of a drama, as his SMB started to head towards the horizon.

As most of the wreck lies below 42m, Im sure the mobile pick-up boat technique with which UK divers are familiar will soon be standard practice. As it was, we took almost the same ascent route back up as everyone else, albeit a little later, but not so late that it cut into our hour of allowable surface interval!

This short time on the surface also severely limited the range of our second dive both days, but lengthy deco stops were livened up by the persistent attention of half a dozen quite aggressive and persistent remoras (shark-suckers), determined to attach themselves to any part of our anatomies they could. Im told it really hurts if one tries to attach itself to your ear. I wore a hood.

MBT Divers has assembled a computer presentation that gives a well-informed briefing on the vessel and I recommend anyone who is going to dive it to watch this first.

The USS Oriskany CVA38 is a very large and complicated vessel, and divers need to know as much about it as possible before finding themselves out of their depth.

The sheer size and majesty of the Big O cannot be easily described. You need to see it for yourself.

Ascending the hard way.
The island superstructure has many levels with open entrances to explore.
The upper works are already attracting masses of fish life.
Inside the control room.