Mike Boon (1940-2014) was a truly legendary caver whose many outstanding achievements included being a pioneer in the use of aqualungs for cave diving which allowed him to pass Sumps 6 and 7 in Swildon's Hole; explorations at the far end of Mossdale Caverns with Pete Livesy; exploring major river caves in Mexico, Guatemala, and Jamaica; and a solo exploration to the far end of Castleguard Cave in Canada which he pushed to a glacial ice plug.

In this interview, conducted by John Donovan and Nicholas Viera, Mike is first asked about the writing of his book Down to a Sunless Sea, and he then goes on to talk about his Castleguard explorations, including the occasion when he and Pete Thompson were trapped by flood waters for two days, which resulted in the de facto closure of all caves in the Banff National Park. He also talks a little about his solo exploration in the cave. The interview was edited by Sid Perou.