But after a period of life trying to understand the vast ecosystems that lie beneath the sea surface, the 73-year-old now becomes the prophet of her extinction.
"It's the beginning of a planetary disaster," he tells CNN. "I was too slow to speak out loud."
In 2016 and 2017, sea heat waves caused by climate change caused a mass bleaching that, along with many others, killed around half of coral at the Great Barrier Reef
"Somewhere between a quarter and a third of all marine animals, there is a part of their life cycle in coral reefs everywhere, "he says. "Well, you take coral reefs and a third to a quarter of all species are wiped out. Well, that's ecological chaos, it's an ecological collapse."