Two big slabs of solid gold hold the chart in place. Captain Rafael Salazar fiddles with a pair of dividers, checks his course, and points to a circle drawn on the chart. Thats the Ines de Soto, he says. Thats where we work today.
It is 6am. We have just left Puerto Esperanza, to the west of Havana. Once outside the port the sea spreads flat and glittering to the horizon. It is going to be hot. We are aboard one of the dive boats of the Carisub team; this one is a converted yacht.
Discovered by Columbus in 1492, Cuba, the largest island in the Caribbean, has long been a menace to ships sailing between Europe and South America. Cubas coral reefs and shallow bays ripped the bottoms out of more than 700 ships between 1600 and 1825.
Treasure galleons laden with silver from the mines of Mexico sailed close to the north-west of the island into the Straits of Florida. More treasure ships from Cartagena in South America had to try to round the islands western tip of Cape San Antonio through the Yucatan Channel.
Pirates, using Havana as their base, preyed on the lumbering galleons. Others were driven by storm on to Cubas north-west coast. Some didnt get that far before running into the coral reefs surrounding the Island of Pines on Cubas southern side.
Travelling together in fleets did nothing to save them from disaster - Spanish records show that 13,000 treasure ships safely skirted Cuba in the years of the 16th to 18th centuries. But the same records also show that dozens failed to make it.
The result is that Cubas territorial waters are a treasure divers dream, covering fortunes in Spanish gold and silver, ingots, coins and jewellery. Not to mention emeralds and rubies by the bagful!
But foreign treasure-hunting divers are banned by order of Fidel Castro, Cubas communist leader and a very experienced diver himself. Not surprisingly, it was his idea to set up a company holding the sole right to dive for and raise the treasures of the Cuban seas.
The Ines de Soto is one of the Spanish galleons that didnt clear Cuba. She struck a coral reef in 1572 when homeward bound from Mexico with treasure for the King of Spain.
No one knows today why she was so far off course. But the spot where she was lost is clearly marked by seven fine bronze cannon, muzzles up to the surface.
Our dive boat drops anchor well off the wreck site, but long before that the divers on board have been arranging sophisticated equipment from the hold on the deck - underwater metal-detectors, airlifts and water-dredges take second place to electronic measuring gear because everything has to be done according to the best archaeological practice.
We are kept back from diving the wreck site itself until the chief archaeologist of Carisub, Dr Abraham Cruz, has carried out a swift survey using a metal detector.
When he surfaces he pushes up his mask, spits out his mouthpiece and shouts happily to those left on board: There is gold down there! A huge pile of it! Believe me!
Carisub carries out its excavations in four stages. First the site is sketched before anything is touched. This is the pre-disturbance survey and can take weeks of work. All objects that can be seen on the surface of the seabed are carefully plotted on to the site plan.
Stage Two involves dividing the site into small sectors. These are gently and methodically excavated, though coral growth often means that the only tools that can be used effectively are hammers, chisels and small underwater pneumatic drills.
Stage Three involves the lifting of artifacts uncovered and plotted. Large lumps of concretition are lifted to the surface in nets for breaking gently open in Havana conservation laboratories.
Stage Four, which is where we are with the Ines de Soto wreck now, means that we can watch and photograph Abraham Cruz using an airlift to hoover up the gold hoard he had located earlier.
The gold coins and small ingots sparkle in the sunlight. They look as though they were made only yesterday. A lot of the gold the Carisub divers find is like this; only rarely does coral cling to it.
Carisub has been searching for treasure-bearing galleons for 16 years now. It has four boats and employs 60 divers, whose skills include archaeology, history, epigraphy (the study of inscriptions) and numismatics (the study of coins).
The young, highly competent men who make up this elite team are all members of the Cuban Communist Party. To be recruited is to be accepted as being upright and trustworthy, devoted to Cuba and not to be tempted by the treasures handled daily.
Salaries are a pittance - around $3 a month. Yet being part of a Carisub crew is a plum appointment in a country in economic crisis, and its members enjoy valuable privileges.
They are housed by the government in a residential district of Havana called Miramar. They are allowed to go abroad - even to the USA - for study trips.
And life on board is pleasant. For these Cubans there is no food rationing and the crew are well looked after by a cook who serves them lobster, beef and rum.
Anyone who tries to intrude on Carisubs territory had better beware - coastguards patrol the islands waters and do not hesitate to inspect fishing boats that linger too long offshore.
Carisubs Director, Vincente de la Guardia, believes the companys monopoly is justified: Wrecks lying in our territorial waters are part of our heritage, as well as being part of the history and culture of the Cuban people. Nobody else will be given a chance to work on them.
He winks hard at Mel Fisher who, for the past few years, has been trying in vain to negotiate with the Castrist authorities for a piece of the action. The American, who became a millionaire through digging up underwater treasure, knows what a boon access to the wrecks would be to his business.
Cubas insistence that the zone is private property is easy to understand, given the results so far. Twenty-one wrecks were located in 1993 alone, following leads obtained from the state archives.
Among the treasures found have been unique pieces such as a solid gold necklace that was to have been a gift to the Spanish Queen Isabelle. It was found on the Nostra Seniora del Rosario, which sank with all on board in 1590, and is estimated to be worth around US $250,000.
After being cleaned and studied in the well-protected Carisub buildings in Havana, all such items are stored in the vaults of the Cuban State Bank.
They remain there until high-ranking government officials allow them to leave. They will find a place in the museums of Havana - or be sent to international auction rooms.
The work of Carisub is expensive, and it is easy to see why. Not only does the crew have to remain at sea for 20 days during each expedition, but the detection equipment is purpose-designed, available only in the USA and Japan, and therefore costly.
Vincente couldnt care less: Do you realise that one days work brings in the equivalent of one million dollars he says. The government gives us everything we ask for, even though the country is going through a period of restriction hitherto unknown.
Fidel Castro, it should not be forgotten, is a man who loves to explore the underwater world. He is an excellent diver and has no regard for cost when it comes to satisfying his passions, of which Carisub is one.
El Commandante is a personal friend of Vincente and dives with him regularly. Castro demands to be kept abreast of Carisubs discoveries, and often visits the crews to encourage them in their work.
Meanwhile, off the southern coast of Cuba at Playa Giron, a small island has for the past 20 years been declared a military zone. It belongs to Castro; this is where he spends his holidays, as Cuban naval vessels patrol the area.
Here, when not contemplating the theory of revolutionary socialism, he allows himself time to dream.
And in pursuit of those dreams the head of this Communist state dives in search of treasure, on two 17th century galleons that he has made his personal property.
PUBLISHED IN DIVER IN DECEMBER 1997
NOTE: Carisub was shut down in 1998 and all underwater archaeological exploration of Cuban waters since then has been controlled by Cuba’s Armed Forces through a body named Sermar.