"I sat on the rock and looked at the whale. Then I felt a tingling in my limbs," Jan Arthur told VG newspaper. "Then I went down to the water where I started to undress myself. I asked a whale expert if he thought it was dangerous. 'Do not jump in the water,' he said. But I jumped anyway."
According to Arne Bjørge at Norway's Institute for Marine Research, Jan Arthur is lucky to have survived.
"Sperm whales are large animals. A single blow with the tail could kill a person," he told VG newspaper.
The 15m sperm whale has been swimming around a bay in the town of Øygarden since Thursday last week, to the delight of spectators.