Slathered in a thick layer of Vaseline and with a hand warmer strategically tucked into his bathing suit, Dobelmann hopes to cross the 64 kilometre lake in under 24 hours, something international swimming association FINA says no other swimmer has ever done.
With marathon training already under his belt, the 53-year-old from Stuttgart told Die Welt newspaper how he turned to long-distance swimming after he got bored of “swimming up and down lanes at the pool.”
From there, Dobelmann went from strength to strength and in 2005 became the first person to swim from Puttgarden on the Baltic island of Fehmarn to the Danish harbour town of Rødby and back, covering the 50 kilometres in around 19 hours.
“What interests me is what my body can do,” Dobelmann told Die Welt. “If your head wants to do something, your body has to follow.”
“I'm a comfortable swimmer,” he said, adding that although he could happily eat a joint of meat, or a kebab before a long-distance swim, during this trial, the unorthodox athlete will be managing on a portion of sugary gel every 30 minutes.
Training for this latest adventure was tough, and in early April it looked like “the Orca”, as he is known to his friends, might not make it, despite his strict training plan of three hours swimming, four to five times a week.
Around six hours into a test swim across the lake he had to be taken to shore. It was raining and the risk of him inhaling water was too high to justify carrying on.
But what Dobelmann did not know, was by the time he was lifted from the water, his legs had been blue for over three hours and he had broken the record for the longest time spent in very cold water.
On Monday, the water temperature was a less intimidating 14 degrees Celsius, and Dobelmann was convinced he would not be giving up – if only because he spent more than €7,000 on the attempt, including a safety boat to accompany him.
“If any of my friends on the boat decide to take charge and lift me out, they know that they'll no longer be a friend of Bruno's,” he told the paper.
Elsewhere in the world of extreme swimming this month, Swiss athlete Ernst Bromeis had to abandon his 1,230-kilometre Rhine swim. Freezing conditions and exhaustion drove the self-proclaimed “water-activist” to throw the towel in at the 400 kilometre mark.
The 43-year-old was trying to raise awareness for water-scarcity issues, while completing a personal challenge.