The water in Labynkyr was +1, +2C under the ice; air temperature was about minus 50C with occasional wind. Picture: Alexander Gubin

Reports of a 'Devil' in Siberia's Lake Labynkyr date from the 19th century, and have intrigued scientists for many decades. The inaccessible lake, in the Sakha Republic, Russia's largest and coldest region, was in March the scene of the deepest-ever dive under ice in the world.

Divers on a joint expedition by the Russian Geographic Society and Diving Sport Federation of Russia reached a depth of 59.6 metres, but their achievement also had a serious scientific purpose. Braving air temperatures as low as minus 50C, and diving under tents erected on the ice, they took samples for examination by scientists which may prove a long-suspected underwater link between the Labynkyr and another similarly mysterious lake, Vorota, some 30km away.

The divers were keenly aware of the age-old accounts of primeval monsters - perhaps relic ichthyosaurs - in both lakes.

Ahead of the trip, the society said: 'Apart from plans to set up a new record for under-ice diving and to perform scientific research, the participants of the expedition want to check those legends about 'Labynkyrsky Chert' - the Labynkyr Devil, a huge monster supposedly living in the lake'.

Maxim Astakhov, the first Russian to win the World Cup in sport diving, an assistant on this expedition: 'I have never experienced driving on Kamaz trucks through the taiga before. It gives you adrenaline. Nobody before tried to dive in such extreme conditions'. Pictures: Anton Raikhshtat

Dmitry Shiller, one of the divers who now holds the world record, admitted: 'We are familiar with the works of scientist Viktor Tverdokhlebov (who in Soviet times gave credence to the monster claims) about Labynkyr lake and of course we did think about that monster when we were there.'

He also revealed: 'We did see mirages there, something like moving islands, but all of us know that it is a common thing in any Northern area with lots of ice and snow, so it is not something special about Labynkyr.'

So what did they find underwater?

'My pictures show what we saw - dogfish', said Alexander Gubin, head diver of Labynkyr trip, president of Vologda Regional Diving Federation, who is also head of scientific diving commission of the Vologda branch of Russian Geographic Society.

'In fact, I photographed these dogfish not far from the bank, in Lake Labynkyr. It was not deep there either, maybe four or five metres. We were just exploring the area near the banks together with another diver, Maxim. This dogfish was about 1.20 to 1.30 metres long, it is quite big for a dogfish, but almost all of this species in Labynkyr are of this size. I saw two more fish like this at the depth of 10 to 12 metres.

'These were the biggest creatures I met in Labynkyr. But know that salmon trout fish can be found there too, and this fish can grow up to 2 metres. I presume some big salmon trout fish could have confused the locals, and this is where the rumours about the monster are coming from.

'Salmon trout is a very strong and active fish, it can actively move in the water and even jump a bit. I believe looking at it from a distance, one may well think something really huge is moving near the water surface.

'We did not see anything big in Vorota either. I am aware of those stories about the monster, but I am a realist. There is surely not enough food in the lake for some enormous dinosaur. So I did not have any weapon when I was diving. My camera is my main weapon.

'Actually I wonder if the lenses telescoping out of my camera, give me a feeling of safety, as if it is a real weapon. But in general I am a brave man, I have been next to a crocodile, and once in the Caribbean off Cuba a small shark attacked my camera.'

Dmitry Shiller, head of the expedition, right before the start. Picture: Anton Raikhshtat

The lake is 14.3 km long, and 4 km wide, and averages 52 metres in depth but has an unusual underwater fissure which reaches down to 80 metres; some 5,000 km east of Moscow, is in the same district of the Sakha Republic as Oymyakon, known as the Pole of Cold, the world's coldest human settlement.

Reports about the 'Devil' or monster date from the 19th century and gained credence from a trip by Soviet geologist Tverdokhlebov to the lake in the Stalin era. He wrote of the 'Devil': 'There have been all sort of hypothesises about what kind of creature it could be: a giant pike, a relic reptile or an amphibia.

'We didn't manage to prove or to disprove these versions, we managed to find remains of jaws and skeleton of some animal'.

Associate Professor of Biogeography Lyudmila Emeliyanova recorded 'several seriously big underwater objects' with sonar readings on a trip to Labynkyr. She is not the only researcher to have done so.

'It was our fourth or fifth day at the lake when our echo sounding device registered a huge object in the water under our boat,' she said.

'The object was very dense, of homogeneous structure, surely not a fish nor a shoal of fish, and it was above the bottom. I was very surprised but not scared and not shocked, after all we did not see this animal, we only registered a strange object in the water. But I can clearly say - at the moment, as a scientist, I cannot offer you any explanation of what this object might be'.

Lyudmila Emelyanova, Moscow State University Associate Professor of Biogeography, working with echo sounding device on Labynkyr, and with the expedition team. Pictures: Andrey Emelyanov

The readings were repeated and she became convinced there was more than one large living object in the pure waters.

'I can't say we literally found and touched something unusual there but we did register with our echo sounding device several seriously big underwater objects, bigger than a fish, bigger than even a group of fish.'

So dogfish or salmon trout or is there something more devilish lurking in these twin lakes? There are certain to be further research trips to find out more.

The March expedition will be remembered for the record-breaking dive.

Bazhena Ostoich, of the World Underwater Federation (CMAS), who was on the trip, reported the success of the dive.

'A new world record of under ice diving was set up by Dmitry Shiller and Alexander Gubin,' she said. 'They dived down to 59.6 metres. This is new world record and I am congratulating Russia and the whole world on it'.

The team reached the the lakes on specially upgraded KAMAZ trucks. The surface was frozen solid - enough to drive the trucks on the ice.

Scientists from Cryolite Zone Biological Problems Institute of Siberian Academy of Science were working with the divers.

The task was to study the hydro system of both lakes, to collect soil and water samples in the coldest season of the year, and also to study the human body activity and diving equipment in extreme weather conditions, with temperatures this winter going as low as minus 60C.

'We were keen to find the crack that is supposed to be at the bottom of Lake Labynkyr, in this case we could have tried to dive deeper, but unfortunately we did not find it. Maybe this is the task for our next expedition to Labynkyr'. Picture: Anton Raikhshtat

Dmitry Shiller said: 'We did several dives at different depths - from open air and from a tent (on the ice). We did one night deep dive. At each lake we cut several ice holes for diving. We gathered water samples at different depths.

'In total, we did about about 200 different measurements and took about 20 samples. The maximum depth we have managed was 59.6 metres.

'Vorota lake is 30 km from Labynkyr. The scientists suspect that the lakes are connected, that there is something like underground tunnels.

'Trying to understand the unique hydro system of these places, we needed to take some samples from Vorota too. The scientists never had such a chance previously and they asked us if we could make it and reach the second lake.'

He stressed that intriguing evidence was found that the claim of the lakes being linked maybe true. Though apart by 30km, their water levels are the same.

'What we found in support of this idea is that the water level of both lakes is identical which made us think about connecting vessels concept'.

He added: The Yakutian scientists are very grateful for our samples. They promise to tell us about the results in three months. I know that they are keen to study the living organisms which can survive in such conditions, and to check what the fish is eating in those lakes because at first glance food supply is very poor there.

'We were keen to find the crack that is supposed to be at the bottom of Lake Labynkyr: In this case we could have tried to dive deeper, but unfortunately we did not find it. Maybe this is the task for our next expedition to Labynkyr.'

'A new world record of under ice diving was set up by Dmitry Shiller and Alexander Gubin,' she said. 'They dived down to 59.6 metres. This is new world record and I am congratulating Russia and the whole world on it'. Pictures: Anton Raikhshtat

Anzhelika Akueva, team member and KAMAZ employee, explained: 'These 30 km took about 20 hours, literally, we were breaking through at a speed of 600 metres per hour. Locals say that the winter is very snowy this year, there is much more snow than usual.'

Gubin, who with Shiller set the new world record of under-ice diving, said: 'Before the expedition we contacted the world community of divers and asked if anybody had experience of diving in such cold conditions. We found out that nobody had it. We had to mix the gases in the conditions of very cold air temperatures and they just were not mixing in the right way.

'So when somebody is asking me if we met that Labynkyr monster, I am saying - mixing those gases was my monster and it was a real one. My mistake in this mixing would have led to somebody's death. We trained in the cold White Sea and managed to go down to 80 metres. There were always some difficulties but we managed well.

'During dives into Labynkyr lake there were no emergencies. But the atmosphere was disturbed, all of us were worrying. For example, once the hoses became entangled, once the wind was so strong that it nearly carried away the tent above the ice-hole.

'The water there is amazingly transparent - just like in Lake Baikal. But of course it was dark at the bottom and we used lights. Unfortunately, we did not meet any unusual creature there, only these huge dog-fish, so please enjoy my photographs.'

Safety coordinator Georgiy Medinin said: 'We took water and soil samples from Labynkyr and Vorota lakes. This was very important for the scientists who study the lakes and nature in this area.

'We will also share our results with other scientists - those who took part in Mars-500 project of a 500 days long 'flight' to Mars. These scientists are interested in the experience of our divers because they study the ability of the human body to resist to the absolutely aggressive environment'.

'When somebody is asking me if we met the Labynkyr monster, I am saying - mixing those gases was my monster and it was a real one. My mistake in this mixing would have led to somebody's death. Picture: Alexander Gubin

Maxim Astakhov, the first Russian to win the World Cup in sport diving, an assistant on this expedition, said: 'I have never experienced driving on Kamaz trucks through the taiga before. It gives you adrenaline. Nobody before tried to dive in such extreme conditions.

'The water in Labynkyr was +1,+2C under the ice. It was warmer than in the White sea where they trained, there it was minus 2C. Air temperatures were about minus 50C with occasional wind. At one time it was very strong wind and it nearly carried away the tent'.

Ali Kariev, head of Magadan branch of KAMAZ, one of the drivers: 'Of course every KAMAZ truck which comes from the factory to work in our conditions must be upgraded. It will be just impossible to use it here without such upgrades, like double glass cab, fuel heating, car batteries heating, extra heating for the cabin.'

Gubin, like others who travel to Labynkyr, feel a magnetic pull from the lake and is keen to return to explore further.

Dr Emeliyanova, from the Biogeography Department of the Geographical Faculty of Moscow State University, feels the same. She remains struck by historical accounts of monsters in Labynkyr and Vorota and believes they are credible.

On the basis of 'sightings' there has been speculation that Labynkyr and Vorota as well as dogfish and salmon trout might be inhabited by a school of ichthyosaurs, prehistoric marine reptiles resembling dolphins or sharks, or plesiosaurs, a popular theory concerning 'Nessie' in Scotland which is often depicted with a long neck.

'We will share our results with scientists who took part in Mars-500 project of a 500 days long 'flight' to Mars; they are interested in the experience of our divers because they study the ability of the human body to resist to the absolutely aggressive environmen'. Pictures: Alexander Gubin

Another version has speculated that relic killer whales could have become marooned in Labynkyr. Some accounts even suggest the 'creature' makes a hideous primeval cry as it attacks its prey.

'Personally, I do believe that when the information about something strange circulates among local people for so many years, it just can't be groundless, it means something is there,' she said. 'I know the local people very well - they are ingenuous but they do not lie,' she said previously.

Now she adds: 'I have been on a dozen expeditions to this region and I can say I know the character of local people quite well. They are emotional - but are not intended to show their emotions and they are very true and honest by nature, often more honest than is necessary. This is why I am not ready to reject all these stories.'

For her another factor is how the stories of monsters in Yakutia relate solely to these two lakes out of more than 800,000 across this giant region.

Soviet geologist Viktor Tverdokhlebov. Pictures: Tverdokhlebovs' family archive

Another account of an entirely separate trip to the lake in August 2006 - where researchers used a Humminbird Piranha MAX 215 Portable fish-finder - produced results echoing her findings. Images are available from this trip, but the identities of those who took part are hidden.

'The conditions were ideal - clear cold fresh water, no big waves, stone bottom without plants there, no engine on the boat, soft and slow moving - all this means there were almost no problems for the scanning,' claimed one of those present.

'Often the device showed the long chain of big fish some 4 meters above the bottom of the lake, when the depth was about 30-45 meters.

'The further we went away from the shore, the deeper the lake was, at one moment there was no fish registered for a long period long, the screen was dead. But all of a sudden it blew up with signals about a huge shoal of fish, just like a cloud.

'Let me say a word about local fish - all kinds of fish here are predators, the bottom of the lake is "dead", stones with sand, very cold near the bottom, no plants. Fish-predators just cannot swim all together making such a huge shoal, anybody familiar with Zoology will understand what I mean.

'This is why it meant nothing else but the huge swimming object with some air inside. We went twice above the object, it was at the depth of 30 metres (where the floor was 50 metres below). The upper 'fish' was at a depth of 25 metres, the lower 'fish' at 32 metres.

'It suggests the object was seven metres wide. What was it? We can't say.

I switched off the 'Fish ID' and we watched just pure scanning.....soon we registered a 'shadow' some 15-17 meters under our boat, it was about 6.5 meters long. It was pretty clear, it was not a fish and not a tree. There cannot be fish that big, and a log would have been registered in a different way. How can it swim under the water?

'The most active 'shadows' or 'bodies' were registered in certain parts of the lake when the depth was 42 to 60 metres'.