British cave diver Martyn Farr to join a team attempting a record for the longest ever cave penetration

Three divers about to enter the impressive entrance of Carwash Cenote in 2000, near Tulum, Quintana Roo, Mexico

British cave diving instructor and photographer Martyn Farr has travelled the world, exploring some of the world's most spectacular underwater caves. He will join a team next month as they attempt to set a world record for the longest ever cave penetration.

Three divers are pictured as they are about to enter the impressive entrance of Carwash Cenote in 2000, near Tulum, Quintana Roo, Mexico

Jenny Pinder swimming through the underwater passages of a spa cave, which has a water temperature of 35 degrees C due to deep geothermal heating, in March 2002 in Grotta Giusti Cave in Tuscany, Italy

Jenny Pinder swims through the tight underwater passages of the Grotta Giusti Cave in Tuscany, Italy. A far cry from the biting chill of British underwater caves, this 'spa cave' boasts waters at a balmy 35 degrees Celsius

Phil Dotchon swimming between mysterious cone-like underwater formations in Mimoso Cave in 2002, in the Matto Grosso du Sul, Brazil. These strange structures are only found in Brazil

Phil Dotchon swimming between mysterious cone-like underwater formations in Mimoso Cave, in the Matto Grosso du Sul, Brazil

Local cave diving instructor, Rony Valencia passing the warning sign near the entrance to the popular Gran Cenote Cave in November 2007, near Tulum Quintana Roo, Mexico

Local cave diving instructor, Rony Valencia passing the warning sign near the entrance to the popular Gran Cenote Cave, near Tulum Quintana Roo, Mexico

Helen Rider swimming into a coral cave at 30m depth in May 2005, off-shore from Hurghada in the Egyptian Red Sea

Helen Rider swimming into a coral cave at 30m depth, off-shore from Hurghada in the Egyptian Red Sea

Helen Rider demonstrates buoyancy control and positioning in this clear underwater tunnel at Dinas Rock Silica Mine in January 2007, in Neath Valley, South Wales

Helen Rider demonstrates buoyancy control and positioning in this clear underwater tunnel at Dinas Rock Silica Mine, in Neath Valley, South Wales

Martyn Farr, the only cave diving instructor in the UK and the country's best cave diving photographer. He will photograph the team undertaking the new world record attempt

These photographs were taken by Martyn Farr - Britain's only cave-diving instructor and the country's best cave-diving photographer. Martyn [pictured above], from Crickhowell, Powys, Wales, will join an international team next month for a world record attempt - the longest ever cave penetration. Martyn will attempt to capture the team - made up of world's best cave divers - as they penetrate deeper into Pozo Azul cave, near Burgos, Spain, than has every been achieved before

Chris Edwards Steve Marsh and Paul Axton carrying remote underwater flash guns to generate sufficient lighting to capture this image, in what is probably the worlds largest underwater tunnel, in Weebubbie Cave in October 2005, in the remote Nullarbor Plain of western Australia

Several sites around the UK, including Somerset, Derbyshire, Yorkshire and Sutherland in Scotland offer cave diving, and Martyn has dived some of the world's most spectacular locations. Included in his collection of photos is the Weebubbie Cave in the remote Nullarbor Plain of Western Australia - thought to be the world's largest underwater tunnel

British cave diving is notoriously dangerous, but Martyn feels learning here can only produce better and safer divers. He said: "Once you can cave dive here you can cave dive anywhere in the world. The systems here are narrow, it's cold and the visibility can be very poor as we have a lot of silt. When silt is disturbed you end up swimming inside a murky cloud and you can lose all sense of direction. All you've got to get you safely out is your guide-line leading you back to the entrance. If people come to me and they can cope here in the Brecon Beacons then they know they can go anywhere"

Andy Chell follows the guide-line through the mine tunnel at 25m depth in February 2006 at Hodge Close Slate Mine near Coniston in the Lake District, England. The tunnel is notoriously silty, and at least three divers have lost their lives in the complex over the years

Although this potentially fatal sport usually requires teams to move equipment and bring safety in numbers, Martyn often ventures below the surface completely solo. He said: "When I am exploratory diving in systems that have not been dived before, I actually prefer being on my own.