'My brother was swept away by tsunami 20 years ago'

Luke Simon's brother Piers died in the 2004 Indian Ocean tsunami while they were celebrating Christmas with friends

A man caught up in a devastating tsunami 20 years ago has recalled the final moments before his older brother was swept away by the water.

Luke Simon, from Somerset, was celebrating Christmas with his brother Piers and their friends in Thailand's Koh Phi Phi resort when the Indian Ocean tsunami hit on Boxing Day in 2004.

More than 230,000 people were killed across 14 countries after the tsunami was triggered by a 9.3 magnitude earthquake off the coast of Indonesia.

Luke said his brother, 33, spent his final moments a hero - hoisting his girlfriend up to safety before succumbing to the "moving landfill" of palm trees, cars and sewage.

Luke Simon (R) said Piers (L) was a "pivotal role model" in his life

The 50-year-old said the disaster changed the course of his life, which he has since spent doing charity work in his brother's name.

"I don't know what I would've done if I hadn't have lost Piers," said Luke.

"He was a pivotal role model in my life. I looked up to him. I respected him. We were very, very close.

"It's changed my life completely, and mum and dad's also.

"I think we're lucky to have created this thing, this charity. It's enveloped our lives. It keeps Piers' memory at the forefront, which I love."

This image of Luke, Piers and their friends was taken on 25 December - the day before the tsunami hit

Luke was teaching at an international school in northern Thailand when he invited the group out to spend Christmas with him.

They were waiting to board a boat to another island when desperate crowds suddenly began barging through the beachfront café in a crazed panic.

Furniture was tossed to the side as their cries of terror slowly grew louder.

"Your immediate instinct is just to follow, we didn't have any chance to process what was going on," he said.

"I had several thoughts, from someone is outside brandishing a knife, to maybe a rabid dog attacking people."

But the truth was much more horrifying. When Luke asked a local what was happening, the man ominously replied "water come, water come".

Nearly all of the island's infrastructure was destroyed in the tsunami

Luke said the chilling realisation that a tsunami had struck the island was "abrupt and instant", like someone had switched the TV channel "from a horror film to National Geographic".

"At that point it changed. We could see what was coming towards us, a boiling mass of water," he said.

"It had already destroyed so many things by the time it got to us it was like a moving landfill, two metres deep and flowing very fast.

"The last thing I remember saying is we needed to be higher, to get off the ground."

The surging water began rising around them, carrying splintered palm trees, telephone poles, concrete blocks, cars, fridges, debris and sewage.

The waves of the tsunami approaching the sand bar of Koh Phi Phi were up to six metres (20ft) above normal sea level

Luke clambered onto a corrugated shed roof nearby and began frantically searching for his then-girlfriend amid the chaos.

"Sophie was pinned by the building and the water rose up and over her body," he said.

"In the end I was just pulling at a hand under the water."

Her life was saved by Piers, who managed to free her from the rubble below and hoist her up, before he was swallowed by an oncoming wave and swept away.

About 850 bodies were recovered from Koh Phi Phi, with a further 1,200 still missing

The remaining friends sat huddled and shaking on the blazing tin roof, waiting in the 30C heat for more than an hour until the swirling water subsided.

"It was a beautiful hot sunny day in paradise that had just completely changed," he recalled.

Luke spent the next five days trawling through hospitals and aid centres in an agonising search for his older brother.

The pair were eventually reunited in a morgue on New Year's Eve, with Piers labelled as 'body number 348'.

The 'School in a Bag' backpacks contain essential school supplies, hygiene products, eating utensils and a sturdy water bottle

A year after his death, Luke and their parents launched the Piers Simon Appeal, to help fund clean-up efforts in Koh Phi Phi.

As momentum grew, they started a standalone charity called School in a Bag, to help disaster victims rebuild their lives and maintain a sense of routine.

Since 2009, it has distributed more than 150,000 schoolbags containing educational supplies to children in 55 countries.

This is the final picture of Piers Simon, captured on Boxing Day morning just hours before the tsunami hit

Luke decided the bags would be red in colour - the same as the T-shirt worn by Piers that morning.

"He was in really bright colours on the last day of his life, and I actually like that," Luke said.

Following on from his charity work, Luke returned to the island in February, to take part in an ITV documentary about what happened 20 years ago.

He said that he felt "a real sense of comfort" being in the last place his brother was alive.

But watching the documentary, he added that it made his "legs go numb and stomach start to churn".

"I was crying. It brought some emotion out," he said.

"I haven't really done a lot of that in 20 years. It was good."