An Otago man was terrified he would be buried alive when a sinkhole opened up under his feet and he fell three metres into the earth.

Andrew Thomson was at his home in Portobello when he went outside on Tuesday afternoon.

"I realised I hadn't fed the fish in a few days, so I popped on down to do so - and immediately fell through the earth,'' he said.

"A fairly harrowing experience, I would say.''

Thomson suffered a few cuts and knocks. But he was mostly worried that no one would hear his cries for help - or worse.

"There was no way to get out, with the mud walls sort of breaking down around me.

"And I couldn't reach the top anyway, so I was pretty well stuck. Tiles just kept dropping every now and then, and, of course, your biggest fear is you're going to be buried alive.

"It was a banger.''

He was stuck for about half an hour, but which felt more like an eternity, he said.

The situation felt even more dire given there were road works happening nearby; therefore drowning his cries for help.

"Really fortunately, a neighbour up the road did hear - I've never met him before. He came on down to investigate.

"He nearly slipped in himself, actually. It started to give way when he got close.

"If he hadn't [found me], I literally would've been there overnight and that was just terrifying."

The neighbour sought help from workers from Fulton Hogan, who managed to get him out safely.

Engineers are now due to investigate the sinkhole today.

Thomson said he would not wish such an experience on anyone else and again thanked the help of the workers and his neighbour.

Despite his ordeal, he said: "A few knocks, but that's alright. Still living the dream.''