The 40-year-old former pro burst into tears after erasing the previous record of 30 hours and 11 minutes held by South African Josh Enslin, braving schools of jellyfish and the night ocean.
The surfer returned to the sand after 17:00 (06:00 GMT) to the applause of hundreds of people who came to support him from Cronulla beach.
The challenge began at 01:00 on Thursday (15:00 GMT), in the light of floodlights. The Australian will have "wrestled" more than 700 waves in total, during series interspersed with rare breaks snacks, sunscreen or eye drops.
At each temporary exit, authorized by the regulations, doctors checked his heart rate and blood pressure before letting him set off again to attack an ocean at 24 ° C, reducing the risk of hypothermia.
Earlier in the day, the record just broken, Johnston had admitted to being "a little burned", but still went back to the water with the objective of 40 hours in the sights.
Australia's Blake Johnston broke the world record for the longest surfing session by chaining waves for 40 hours off a Sydney beach © Saeed KHAN / AFP
At 19:00 (08:00 GMT), the surfer, whose father committed suicide 10 years ago, had allowed, according to the site of the event, to collect more than 330,000 Australian dollars (208,000 euros) in favor of prevention around suicide and mental health among young people.
He originally planned to raise funds by running 1,000 kilometers, but fell back on surfing when he learned that the record was "only" 30 hours.
According to his brother Ben, the forty-year-old had prepared for many obstacles, including a possible one... shark attack. Without being worried.
"I surfed at two o'clock in the morning with him and the lights went out so it was complete darkness," he told national broadcaster ABC, adding that there was "a bunch of jellyfish" in the water.
This isn't the first time Blake Johnston has embarked on an endurance marathon: in 2020, he ran 100 kilometres along Sydney's rugged south coast, breaking down most of the distance barefoot.
© 2023 AFP