A desperate determination to see his wife and children again has been credited with helping to sustain a man as he was trapped for hours in a dam on the NSW Mid North Coast this week, with just his nose and the top of his head poking out of the dirty water.

Daniel Miller, 45, remains in John Hunter Hospital in Newcastle in a stable condition following his incredible ordeal at the property in Charlotte Bay, about 25 kilometres south of Forster, on Tuesday.

Mr Miller was driving a three-tonne mini excavator when the banks of the small dam gave way and the machine toppled into the water. His family says he was trapped beneath the excavator's roll bar for five hours, as his feet slowly sank in the mud.

Just how he managed to arch his back and keep his nose above the waterline, while sporadically yelling out for help, left his family and emergency service workers stunned. One firefighter said the weight of the excavator pushing on Mr Miller's back meant he was virtually doing a push-up for hours.