Terry Kerby has been described as the most experienced submariner on the planet.
He has been piloting submersible vehicles since the mid-1970s, allowing him to get up close to some of the ocean's deepest trenches and the most remarkable undersea landscapes.
He is the director of the Hawaii Undersea Research Laboratory, known as HURL. Much of his work has been done in the waters around Hawaii, in his submarine, Pisces V, which he has also piloted in a survey of the volcanoes in the Kermadec arc, northeast of New Zealand.
The scenes he get to witness are so remarkable, he has created his own illustrations of the undersea pinnacles and volcanic vents - because, he says, the limitations of light and space make them impossible to properly photograph.
He talks to Kathryn Ryan about his undersea career.
Terry Kerby will be speaking at the upcoming Kermadec Science Symposium in Wellington next week (April 11)