I STOOD ON A CURVE OF SAND AS THE SHADOW OF AN ANCIENT TEMPLE crept along the foreshore, following the sunrise on the horizon. Beside me was my dive gear, in the middle distance a crew of dark-skinned fishermen readying their craft to take us on a dive that might just turn local myths into history.
 It had taken more than a year of frantic administrative activity to reach this point. Mahabalipuram, on Indias east coast south of Madras, is an area steeped in folklore as well as religious and cultural heritage. Fishermen had spoken of temples beneath the sea, historical records referred to the area as The Seven Pagodas, yet only this one temple remained on the shore. Were the others lying beneath the powerful swell that battered this coast
 Every expedition needs a spark to drive it through the dark logistical days. Ours had come in the form of Graham Hancock, the international best-selling author and investigative journalist.
 A diver himself, Graham had long held that flood myths and legends of lost cities and civilisations should be taken seriously.
 So when the Dorset-based Scientific Exploration Society approached him to discuss a possible collaborative project, he quickly identified this area of coastline as rich in possibilities.
 Graham had amassed and finally married up scientific data and local myths to pinpoint Mahabalipuram as the potential location for accessible submerged ruins. Now he was with us to dive the site and see whether his theories would stand up.
 Accessible is a relative term. We had our target area; now we had to put together an expedition in a region with no diving infrastructure.
 Requests for compressors resulted in furrowed brows, decompression chambers in stunned silence, and oxygen in a gigantic rusting cylinder containing what appeared to be industrial O2. The only boats available were huge, high-sided, wooden trawlers which rolled wildly in the slightest swell, or smaller tenders powered by long-shafted diesel outboards, the props of which would spin sickeningly in mid-air as the local skippers manoeuvred them around nervous divers.
Fortunately we also had the divers of the Indian National Institute of Oceanography alongside us in the build-up to the project, led by the piratical figure of lead diver Sri. His encyclopaedic knowledge of local tides and conditions was invaluable, especially when combined with the expertise and diving skills of Sundaresh and Dr Guar, the NIOs resident diving archaeologists.

archaeological worms
The expedition was to be in two parts, the first an investigation and survey of a large U-shaped structure 2 miles off the coast of Poompuhur, more than 100 miles south of Mahabalipuram.
 Mentioned in Grahams book Underworld, and in his TV series Flooded Kingdoms of the Ice Age, should it be proved to be man-made its 23m depth would indicate extreme antiquity, and open a can of archaeological worms about civilisations origins.
 In late March the team assembled on the beach at Poompuhur, eyeing the approaching skiff nervously as it slewed through the swell.
 The support vessel for this phase, a 54ft local trawler christened The Death Star by the team, swung and rolled like a wild animal on its mooring. This would be no diving holiday.
 We pounded through the Indian Ocean for 40 minutes and anchored over the site. Green-gilled divers assembled their gear in the sweltering heat as the boat lurched drunkenly around them. A glance over the side revealed a snorting current, and visibility looked mediocre at best. The answer to the mystery of this structure, standing proud of an otherwise featureless seabed, would not come easily.
 The first divers down reported an angular structure draped in fishing nets and monofilament tendrils. For two weeks our divers crawled over this mysterious mound, measuring, photographing, filming and chipping. Although only at 23m, visibility was under 5m, a blizzard of careering suspended particles.
 Divers were allocated into strict teams, with a tender and a supervisor; checks were carried out by both supervisor and divers; and a standby diver paced the tilting deck, nervously awaiting a barked order from the deck marshal.
 Reassured by this matrix of safety, I fastened my gear with racing heart and a sense of expectancy. Would I see the font of civilisation or simply another reef
 My first impression as the object appeared out of the gloom was of disorientation. Naively, I had expected a view of angular corners and lines of masonry. What greeted me was a jumble of coral overgrowth and rounded boulders.
 This is the dilemma of true antiquity - should this structure be as old as Graham believed it to be, some 11,000 years, it would be buried under coral, worn smooth by vicious currents, and battered by the years it would have taken to disappear beneath the waves. So the older it is, the harder it is to tell its origins.
 After three weeks and 100 dives of intense surveying by a team with a wealth of diving experience, the conclusion was that the structure had been shaped by man.
 I even had one sheepish Indian archaeologist sidle up to me one evening to say that, in his opinion, the structure was definitely man-made, but that he needed that final definitive piece of proof before committing himself to the record. The mysterious structure wasnt a U-shape at all, more of a giant question mark.

crackling breakers
On to phase two - the journey up the coast to Mahabalipuram meant moving lock, stock and two smoking compressors over terrible roads in baking heat in a knackered lorry. We had given ourselves only three days to explore the site.
 Here the problem was negotiating the great rolling surf that pounded the foreshore. There were no sleepy inlets or quiet harbours at Mahabalipuram - the fishermen braced their legs on sturdy wooden rafts and charged the breakers on the way out to sea, squinting through streaming foam.
 The return journey meant hissing down the faces of crackling breakers, staying just ahead as the wave tried to grab you with its white crest. Doing this while sitting on a pile of dive kit, cradling your camera in one hand and holding on for grim death with the other, left me not knowing whether to laugh or cry. All diving should be this way!
 Our three boats moored over the first site, a thrilling combination of darkened water and swirling foam covering a huge square rock that almost broke the surface. The first two divers (fittingly an Indian and British buddy pair), vanished beneath the waves. A signal was passed up the safety line that all was well, and the rest of the team followed in waves. What we found would resound around the world.
 Immediately apparent on the seabed were great blocks of masonry, some standing in neat rows, some jumbled in mute testimony to the power of these waters. The focal point for these blocks appeared to be great stone monoliths, angular corners still visible, rising proud of the seabed to the surface 7m above.
 Here there would be no furrowed brows or dusting for elusive archaeological fingerprints. Man was everywhere, in the lines of huge blocks curving in an elegant wall, in the lip of a large area of worked stone glimpsed through the sand, an exquisite line disappearing beneath the substrate leading to who knows what
 Some blocks, protected from wave action by the proximity of others, were carved so precisely that they could have been laid down the previous day.
 Despite the shallow depth, diving this area was fraught with difficulties. Not only was the trip out hair-raising, but mooring presented new dangers. The anchors were primitive wooden hooks, and dragged quickly through the sand as the boats, weighed down by divers, fought the muscular swell.
 In the water, we had to dance and spin around the structures in the surge, warily eyeing the razor edges of mussels and barnacles that caught many a finger and water-softened palm.

gigantic sugar cubes
The scale of what we were diving soon became apparent. Divers would enter the water only to emerge several hundred metres away, explaining hastily to outraged supervisors that they had remained on the ruin field throughout their dive, and surfaced with it stretching into the gloom before them.
 More than once I would take several fin-strokes away from a central structure before turning to take in the entire view, only then realising that I was looking at right angles and great stone blocks, huge steps and flat platforms.
 The four large central structures were surrounded by a glorious jumble of blocks and low walls, looking like gigantic sugar cubes with neat corners and flat surfaces. Each vast block was separated from the others by hundreds of metres.
 Divers would come across random blocks and worked masonry, indicating smaller structures separate from these main focal points. Any attempt to identify an overall pattern was futile as time ticked away, but the lasting impression was one of scale.
 While we focused on the central structures, I would speculate that divers could have dropped in on any point in the surrounding area and still found evidence of man-made structures. The fishermen indicated two further reefs considerably further along the shore (making a total of six - our elusive six temples).

granite shrine
The ancient temples in the area were classically built using sandstone around a central granite shrine. Could we have been looking at these central shrines, with the sandstone washed away long ago
 Such speculation was fuelled by one of the dive teams discovering an angular entrance in one of the blocks, similar to the doorways to shrines found on the shore.
 Time seemed to accelerate as we dived, each team returning with eyes popping and further tales of jumbled ruins. We had merely scratched the surface when our three days were up.
 A well-funded expedition is now needed to map the extent of the ruin field, explore the glorious tangle of masonry on the seabed and reveal the secrets beneath.
 We hope to return and, with the experts from the NIO, start to untangle some of the mysteries, the biggest of which is the age of the ruins. Experts in sea-level rise and tectonic activity from Durham University have speculated that they could be 5-6000 years old, predating the earliest civilisations and making this site an area of truly international significance.
 My abiding memory on the final day was of a broad smile from one of our skippers. On seeing my stunned reaction to our find, he extended a brown arm towards the monstrous swells further out to sea and said: Ah, but the really big ruins are out there. Who knows what secrets remain off Mahabalipuram

The single temple at Mahabalipuram
Monty Hall briefs a team made up of members of the Scientific Exploration Society, Indias National Institute of Oceanography and locals
part of the underwater remains at Mahabalipuram
getting out through the breakers was often tricky
NIO chief diver Sri
Graham Hancock, seen left with Monty Halls
a diver in the swell at Mahabalipuram
Surveying the U-shaped structure; and blocks on the seabed at Mahabalipuram