As the earthquake struck, a Christchurch lifeguard could only watch in horror as a cliff began to collapse just above the youngsters he was supervising - including his son.
Craig Jamieson, the Taylors Mistake Life Saving Club patrol captain, was looking after 12-year-old son William and four other rookie lifeguards as they took part in a cliff-jump exercise.
Mr Jamieson was in a rescue boat in the sea below when he realised that what he thought was maybe a dolphin bumping his craft was in fact an earthquake.
"I'm in a boat that's sitting in water and it's completely out of control, to a point that I'm nearly falling out of it. That's how much movement there was in the sea," Mr Jamieson said.
"I can hear the noise, then I look up and I can see the cliffside falling over these guys. There's just this huge noise."
Mr Jamieson only had eyes for the youngsters on the cliff, where they struggled to figure out what to do - whether to duck into a cave behind them or jump into the water.
"I'm thinking, 'These are the kids of my best friends.
One of them is my wife. F***'."
He made a split decision, shouting to the youngsters to jump into the sea.
"I'm just trying to figure out - do I get them back in the cave, or is the cave going to collapse? Or do I get them in the water? So I'm saying, 'I want you back to me! Just get in the water!'
"At least if the rock's falling, the water's going to protect them."
One of the youngsters decided to run back down the cliff, while the others - including William - dived into the sea.
It was then that Mr Jamieson saw a piece of rock "as big as a microwave" narrowly miss William.
William, a pupil at Sumner School, described the moment the rocks started "swaying".
"I just saw all the rocks come down. My mates were yelling, 'Get out, get out!' Then dad was yelling, 'Get in the water!'
"I jumped into the water and went under and I just thought, 'God, that was a dumb idea.' All I've been told is I almost got killed by a rock the size of a microwave. I got away pretty lucky."
William, who wants to be a police officer one day, said although it was big experience, he was not feeling scared.
"I feel pretty all right because most of Christchurch is pretty used to it now."