The annual charity Birdman Rally is held at Melbourne's Yarra River, and involves participants flying homemade gliders in front of thousands of spectators.
Contestants jump off a four-metre (13-foot) platform above the river, staying in the air for as long as possible before crashing into the water.
This year's contest attracted 15 competitors, including a man dressed as the Bride of Frankenstein, a woman flying a horse made from balloons and another wearing a pterodactyl costume.
"I was really worried about the weight of the 'boob chute' so I decided to kind of ditch that, commit to a forward roll and just never come out of it," he said.
Mr Johnson also raised more than Aus$20,000 (US$15,000) for a cancer charity set up after his sister was diagnosed with the illness, the Australian Broadcasting Corporation reported.