When was the last time you found a bronze cannon, more than 3m long and weighing nearly two tonnes For myself and 11 colleagues, it was in April of this year on the far-flung British dependency of St Helena, in the South Atlantic, 1500 miles off the coast of Africa.
One of the aims of our expedition to this tiny island was to dive on the site of the wreck of the Witte Leeuw (White Lion), a Dutch East Indiaman that sank in Jamestown Bay in 1613.
Picture the scene: three inflatable boats are moored over the approximate site of the wreck, and the first three pairs of divers enter the water. After 20 minutes, they all return to report that they have indeed dived on the remains of a wooden ship protruding from the fine sand at a depth of 35m, and on top of the sand are three ferrous cannons ­ in short, a site that offered some promise.
Meanwhile, the anchor on one of the boats has dragged and then snagged on an obstacle. The divers from that boat descend, intending to free the anchor, then find their way to the wrecksite.
But by the time they reach the anchor it has freed itself and they are mid-water, with the bottom visible below but too deep. They free swim, following the slope up to shallower water.
Once they are at 35m, they profile along the sand in the hope of finding the site. But after 12 minutes they still havent found it, although at the edge of their vision something appears to be sticking out of the sand.
Knives are unsheathed and a quick scrape of the protuberance reveals it to be made of bronze.
Did we believe them when they surfaced Not likely, and as it had been the second deep dive of the day, we would have to wait until the following day to confirm the find.
Such was the accuracy of our transits that the first pair of divers into the water the next morning confirmed the find within two minutes of leaving the surface, after which another five pairs of divers photographed or cleared away some of the sand around the cannon.
Due to the lack of recompression facilities and no prospect of evacuation ­ because the island has no airfield ­ we restricted ourselves to a 40m maximum and no decompression diving, save for precautionary stops.
We reported the find to the Governor of the island and after some discussion it was decided that we could recover the cannon ­ an exciting but daunting prospect for us. After all, while we had all carried out lifting exercises before, no one had done one on something so valuable, or under so much scrutiny.
While preparations were made, some of us investigated the possible source of our find. The White Lion was in a party of four ships on her way home to the Netherlands from the Far East with a cargo of spices, porcelain and diamonds.
On arriving at St Helena to take on supplies, they came across two Portuguese carracks at anchor in the harbour ­ the Portuguese and Dutch were not the best of friends.
The Portuguese put up a better fight, sinking the White Lion and severely damaging another. The other two Dutch ships quickly fled, bruised but in one piece.
That was the last of the White Lion until Belgian salvor Robert Stenuit managed to find the wreck in 1976 while following up on his research. He recovered much of its porcelain and some of the bronze cannons.
After his successful salvage operation, which was reported in National Geographic in November 1978, the site was left alone, save for the occasional dive by islanders. So our find was a complete surprise, not only to ourselves but to the island as well.
It took three days to recover the cannon, which had to be dug out of the sand. Progress was hampered by a gentle current that filled in our excavation work between dives.
Even with three one-tonne bags fully inflated, the sea was reluctant to give up its treasure. Only after some vigorous rocking by a couple of the divers did the cannon commence its ballistic rise to the surface.
The three large orange lifting bags breaking the surface was a spectacular sight. Immediately, one of the boats moved in to secure a line to our precious load.
Then we started the slow drive back to the quayside which, remarkably, was only 500m away ­ such a treasure so close to landfall.
The Elation is an understatement of what we felt at that time, and the true beauty of our find wasnt realised until we had rested the cannon by the quayside ready to be lifted by crane a couple of days later.
We dived the now shallow site to take a closer look and marvel at the cannons condition. There was little encrustation, the lifting eyes were in the shape of leaping dolphins, and we could make out writing which appeared to be Dutch. Even the date of manufacture wasthere: 1604.
The last phase of the recovery was on to the quayside so that we could present it to the Governor and the island. With the exception of the crane having to bounce the cannon closer to the harbour wall so that the cranes reach could manage the load, everything went smoothly. After about 20 minutes, a beautiful bronze cannon was mounted on to a gun carriage for all to marvel at.
The cannon is currently being kept in a freshwater tank on the quayside and regularly flushed out. The intention is to put it on permanent display in the public gardens once restoration work is complete.
Despite an extensive maritime history, the island being a favoured stop-over point for ships of all sizes and origins prior to the opening of the Suez Canal, St Helena sadly lacks evidence of its maritime heritage. This cannon, we hope, will go some way to rectifying that.
The project recently achieved a prestigious runner-up award in the Duke of Edinburghs Prize, which recognises the best underwater scientific projects carried out by BSAC members.
Would we go again Too right. There may be other cannons, porcelain ­ even those diamonds. There are also the other wrecks we briefly explored, and there is a story about 23 ships that went down in Jamestown Harbour one stormy night during the last century!