His mission requires courage, skill and supreme fitness. Even wearing a 5mm thick wetsuit he will have to overcome bone-numbing cold to reach the record depth of 75m. Christian set the current record of 65m at the same lake 15 years ago.

“The biggest challenge is the temperature,” he says. “Everyone knows the phenomenon when you get in a very cold shower, or in a cold pool after a sauna. The lung volume is reduced by a third because everything is tight in the body.”

The bitter cold means Christian, who has been training for the February 24 dive for six months, can’t “warm up”. He must start his record attempt without delay, before the frigid air makes his body too cold.

With a support crew of five divers, the man dubbed "The Iceman"  will also be wearing an invaluable tool, a special Edox Sharkman II diver’s timepiece, one of five in a limited edition collection.

The Lake Weissensee cold won’t be a problem for the Sharkman II; it is water-resistant to 1000m and the rugged steel case and scratch and shock-resistant ceramic bezel can handle even the most extreme environments. Just 300 are available worldwide.

The Sharkman II’s case back is engraved with a shark motif, a nod to The Iceman's efforts to help protect species worldwide and also symbolic of his connection to the mysterious Greenland Shark - a master of its deep, icy, domain just like Christian Redl.