Hidden dangers:

A shipwreck is often the only thing standing up from a flat seabed plain. Consequently, it becomes a magnet for all kinds of fish, shellfish and other marine life. Big conger eels live in most shipwrecks. Lobsters call them home. So do big crabs. And huge shoals of pouting and pollack are always to be found circling around.However, there are serious dangers that must be watched. There is little danger from sealife as big congers will not attack you, nor will big lobster or crab unless you put your hand in their claws.

The real dangers are the depth and the time spent underwater which must never be forgotten. Decompression sickness - the “bends” - is always waiting to strike divers who break the rules and make fast ascents from deep wrecks. The British Sub-Aqua Club has always recommended 50 metres as the sensible limit for experienced amateurs diving using compressed air. Wreck divers should stick to that limit, even though modern gas mixtures appear more tolerant than compressed air. They should be wary too of their depth when exploring the ship. The inside may be much deeper than the outside if the ship has sunk into a soft seabed.

Wreck diving is not for the inexperienced and has it’s own special dangers. Like all amateur diving, it is never carried out alone. There is the risk of running low on air due to becoming absorbed in exploring the wreck, or getting entangled in a fishing net (sometimes many nets are draped over one ship). The wreck diver is bound to consider exploring inside the wreck if a suitable hole or entrance is found. However wreck penetration is the most dangerous part of this kind of diving.

Even swimming under a piece of wreckage is dangerous. Hanging wreckage may be so unstable that it will fall because of the disturbance which is caused by the diver’s exhaust bubbles or fin movements. One diver on a wreck recently was trapped by a steel door falling on him and pinning him to the seabed. He was saved by the prompt action of his buddy diver.

Forbidden wrecks:

A number of divers have died trapped in wrecks. Silting of a wreck takes place very quickly after her sinking. This makes it very dangerous to enter a wreck without some foolproof method of return to a clear exit point. One such method is a lifeline. A few fin strokes inside a wreck are enough to turn visibility into absolute zero. In that black cloud, even the powerful torches which every wreck diver carries, could not show them a way out to the open sea. Wreck penetration is not a spur of the moment thing. It has to be carefully planned in the same way as cave diving.

There are certain wrecks that are protected by law. These are wrecks of historic importance and “War Graves”. Forty-eight wrecks dating from a Bronze Age galley to a submarine of 1880 are designated under the Protection of Wrecks Act of 1973 and all diving on them is banned without special permission. A classic example of this kind of wreck is Henry VIII’s flagship Mary Rose, sunk in 1545. After being found by amateur divers, she was protected until raised and put on show at Portsmouth. It is also possible to see some protected wrecks through the Nautical Archaeology Society.

The Military Remains Act of 1986 puts other restrictions on some wrecks of ships and aircraft “known to contain remains of service personnel”. Though divers may visit these “war graves”, it is only on a look-but-no-touch basis. Divers may not enter such wrecks, disturb them or remove any artifacts.

Wreck divers like to collect souvenirs from wrecks but every item recovered from a wreck must be reported to the Receiver of Wreck at the Coastguard Agency in Southampton. In the case of a small fairly modern item, such as a porthole, the diver is usually allowed to keep it. Other more valuable items are held by the Receiver for a year and a day and, if not claimed by their owner during that time, become the property of the Crown. They then may be auctioned. In such a case the diver is entitled to a salvage award from the proceeds.

A recreational diver who explored the seabed off Shag Harbour, N.S., where a UFO is alleged to have crashed in 1967, says what he saw last month can’t be explained.

David Cvet and a diving buddy came across a couple of dish-shaped depressions, each about six metres in diameter. The ocean bottom anomalies were found 11 fathoms, or about 20 metres, below the surface, in the spot where witnesses say an alien craft swooshed low over the Shelburne County coast.

“In the depression itself, it was as if somebody had come by the day before and swept it clean,” said Cvet on Friday during the Shag Harbour UFO Incident Society’s second annual festival and symposium.

He said the depression was lined with pebbles about four to six centimetres in size. The surrounding seabed had large rocks and pebbles and vegetation.

On Oct. 4, 1967, several witnesses described seeing something crash into the sea off Shag Harbour. In fact, people as far away as Yarmouth, N.S., reported seeing something streak across the night sky.

There were no reports of aircraft in trouble that evening, even though a patch of yellow foam about seven centimetres thick was seen on the water off Shag Harbour not long afterwards. The incident has been listed as a UFO crash.

Cvet, who’s from Toronto but summers in Smith’s Cove, N.S., said he’s known about the Shag Harbour UFO incident for many years.

“I think (it) has enough compelling evidence to warrant further investigation,” he said.

On July 20, Cvet used a copy of a 1988 report from a bottom sonar sweep of the area that found four dish-shaped anomalies.

He and a friend worked out the co-ordinates and planned their dive.

“We left from Lower Woods Harbour and came down to this location and dropped a buoy overboard,” he said, tracing the boat’s 25-minute trip on a map with his finger.

The divers entered the water just before 2 p.m., about 10 minutes before low tide. It was a pleasant 24 degrees on the surface and about 16 degrees at the bottom.

“The water was pretty much like pea soup,” Cvet recalled.

Nevertheless, they soon came upon the first of two depressions.

A French pirate ship, that preyed on rich merchant vessels in the seas around Indonesia in the early 19th century, has been tracked down by a German treasure hunting duo who believe it may have a cargo of gold on board worth more than £50m.

Martin Wenzel and Klaus Keppler estimate that the ship had been carrying a cargo of two tons of gold. Its value would far exceed their haul from a sunken British buccaneer, the Forbes, last December which yielded silver worth close to £7m.

Much depends on the gold coins aboard the new wreck off East Timor and their rarity, plus any additional riches which the raider may have picked up on her travels in the early 1800s.

“I can’t tell you its location for obvious reasons but we are very excited,” said Wenzel, 42, a self-made millionaire from former East Germany.

“We think we know where it lies exactly, near East Timor. We’ve found clues in shipping archives about its cargo of gold. But we don’t yet have the salvage license. They are extremely expensive and the political situation there is difficult.”

He is scheduled to fly from Germany at the end of the month to supervise the search.

Wenzel is an unlikely treasure hunter in the waters off Indonesia. He grew up in the landlocked city of Weimar under communist rule. As a schoolboy he made a Jolly Roger flag while devouring books on pirates and their treasure.

After the fall of communism he made a fortune in property and gambling machines, allowing him to revive his boyhood dreams. In 2007, aged 40, he met up with Keppler, now 70, a fellow engineer and diving enthusiast.

They decided to get serious about the salvage business. One year later they founded Nautic Recovery Asia after investing close to £3m and set about scouring the seabed off the coast of Indonesia.

The Forbes, which ran aground on a reef off Belitung Island, between Borneo and Sumatra, on September 9, 1806, was discovered by accident. The crew of 50, including 25 divers, several ship hands, three Indonesian army soldiers aboard to ward off modern-day pirates and experts who study the maritime archives, was searching for another vessel called the Gypsy of London when the Forbes was found in 125ft of water.

“From the local fishermen we knew there was something like a reef with a lot of fish around there,” said Keppler. “Down went the diver and found it.”

Wenzel added: “We brought up wine still in bottles, gold jewellery, crystal, silverware and pewter plates. These men on board, they knew how to live well.”

The Forbes was captained by Frazer Sinclair, from Stromness, Orkney, and sailed under a commission from King George III - “a kind of pirate with a royal permit”, said Wenzel.

Sinclair and his crew survived the wreck after putting to sea in three lifeboats. The Forbes had carried opium and iron from Calcutta to the far east and was, according to the Asiatic Annual Register, on its way home carrying a “considerable amount” of loot and cargo. It met its fate shortly after the men boarded and looted a Dutch vessel, which ran aground at the same time.

The bounty from the Forbes, and from a Chinese trading vessel from the 10th century which yielded some 15,000 beautiful ceramic tiles, sits in a Jakarta storehouse under guard until buyers are found. Every artifact found is logged into a computer data-bank and the Indonesian government takes 50% of the profits.

It is rumored among treasure hunters that local officials are not averse to cutting individual deals. But according to the team it is rival treasure hunters who must be watched most closely.

“We have to guard the area around the spot. If not, illegal divers will steal the goods,” said Keppler.

He hopes the Indonesian government will set up a museum from the remnants of the Forbes, which was a fine ship built in the Calcutta dockyards around 1802.

Horst Liebner, an expert on Malay culture and history, said the Chinese ship known as the Karawang Wreck was a “time capsule”.

He added: “In Germany such a find would be a sensation, but in Indonesia not a single archeologist stopped by to have a look.

The remains of the Air France jet which went missing over the Atlantic on Monday are in very deep water, making the job of finding them extremely difficult, not to mention any attempt to salvage the aircraft and the bodies of those who were on board.

A French government minister has said the black box flight recorders are believed to be at a depth of between 3,660m (12,000 ft) and 3,700m. At this depth, pressure is immense and there is no daylight.

Any search to locate the flight recorders and any plane wreckage will involve a number of technologies. Below we outline the main methods of salvaging wrecks, from divers to the latest deep sea exploratory vehicles.

Scuba diver: US Navy divers were used to retrieve bodies and light debris from TWA flight 800 which crashed into the Atlantic off New York in 1996. The plane was discovered at a depth of 40m, within the maximum operating depth for divers which is typically 50m.

Bathymetric survey: This is a sonar device placed beneath a ship that would sail in a designated pattern over an area to map the seabed. It “looks” straight down to produce a 3-D map of the seabed but can only operate up to a depth of 1,000m.

Pinger Locator System: This is a specialised listening device that is towed at a depth of up to 4,000m by a ship. The device listens out for the sound of the pinger which is part of the flight recorder. It is activated on contact with sea water and every commercial aircraft carries one. It will emit a signal for up to 30 days.

Side Scan Sonar: Once the pinger is located, a more detailed survey of the area can be carried out. The SSS is a cigar-shaped tube that is towed by a ship to map the seabed in a designated pattern. “You attach it to a cable and you mow the lawn,” says Tim Janaitis, Director of Business Development at Phoenix International, a specialist marine salvage company. Mr Janaitis said he believed only the US Navy had the sophisticated pinger locator system to operate at the depth the Air France aeroplane is believed to be.

Remote Operated Vehicle: These are highly sophisticated yet robust underwater vehicles that can operate at depths up to 6,000m. They have video and powerful lights to illuminate the gloomy deep waters that they operate in. They can also have mechanical arms attached that allow the ROV to pick up bits of debris or attach straps to enable a ship’s winch to lift the item to the surface. Phoenix International says it has raised a portion of an Israeli submarine weighing 3,600kg from a depth of 3,000m. The US navy has raised an entire helicopter from a depth of 6,000m.

Mini submarine: France has dispatched a boat with a mini-submarine, the Nautile, aboard. This can operate at a depth of 6,000m, but it was not expected to reach the zone until early next week.