A moment of dazed silence ensued as those on the beach processed the news, followed by a terrifying scramble for shelter.

"Suddenly about 50 phones went off around me on the beach," Ms Smith said from Hawaii on Saturday afternoon.

"Everyone's just looking around me going, 'What do you do? What do you do?'".

The shore at the Banzai Pipeline was busy on Saturday morning, with those eager to watch the huge swell coming in at the famous surf break.

It was 8.07am local time when the alert came through. It read: "Ballistic missile threat inbound to Hawaii. Seek immediate shelter. This is not a drill."

Ms Smith, who works as a photographer for Fairfax Media in Sydney, had been on holiday for about a week-and-a-half with her husband, Nick Conrick, their eight-year-old son, Nixon, and 13-year-old daughter, Ebony.

The family drove from their accommodation at Waikiki at 6am to catch a glimpse of the famous swell.

"We were pretty much helpless, standing on the beach just going, 'What the hell do you do?'" Ms Smith said.

As reality set in, they desperately sought out locals for advice on what to do, but many were just as clueless. Eventually someone herded them into the local school, Sunset Beach Elementary School, where they "bunkered down", with nothing left to do but wait.

"We were just sitting in there and literally it was just silent, no one was talking," she said.

"It was just fingers crossed, I guess, just sitting there waiting."

Ebony had received the alert on her mobile, and Ms Smith was able to screenshot it and send it on to her father in Australia.

At 5.10am her father woke to the news, with two short messages from his daughter, "Check news", then, "We can't".

Ms Smith's father scoured the internet and turned up nothing, assuring his daughter that it was a false alarm.

But even though "things weren't adding up", there was still no formal confirmation that the missile threat was not real. It was about 35 minutes of waiting for Ms Smith before another text message came through to confirm the alert was false.

Shock was the main reaction to the alert being cancelled for those in Sunset Beach Elementary School. For 38 minutes, people around Hawaii earnestly believed their world was about to be turned upside down.

"It was still a bit of disbelief," Ms Smith said of the moment the threat dissipated in the same way it had arrived, on phone screens around her.

Rumours flew about what had happened, and Ms Smith said it took a while longer to find out "it was human error".

David Ige, the governor of Hawaii, told reporters on Saturday someone at the state emergency management centre pushed the "wrong button" during a shift, CNN reported. The US Federal Communications Commission said it would launch a "full investigation" into the accidental alert.

The incident took place amid mounting international tensions over North Korea's development of a ballistic nuclear weapon.

"I'm glad it was human error, but how could this happen?" Ms Smith asked.

"My eight-year-old son was just sobbing, I'll never forget the look on his face.

"All my son wants to do is go home - he's asked a lot of questions about North Korea today."

Ms Smith said it's been "the talk of the town", and despite the trauma "there's a lot of grateful people today".

As the sun went down over a beach at Waikiki on Saturday evening, people clapped, glad to have made it through the day.

with Reuters