Unfathomable beauty, unlimited coconuts, uncrowded waves – it's little wonder the island chains off Sumatra have become a surfer's paradise.

The resort island of Pinang where Elliot Foote and his mates were heading on Sunday to celebrate his 30th birthday promised a "castaway lifestyle" — and it delivered. The twelve friends were travelling on two wooden speedboats from Nias to Pinang, in the Banyak Islands, on a ten-day surfing trip when disaster struck.

One of the boats managed to seek refuge and made it to a nearby island; the other, carrying Foote, his girlfriend Steph Weisse, and five others, lost contact. Many feared the worst for the four Australians and three Indonesian crew members onboard but after being lost at sea for more than 36 hours, all but one were found alive.

When two wooden boats set off from Botolakha jetty on Nias island, none of those on board could have predicted what was in store (ABC News: Mitch Woolnough)

Foote, the last to be pulled from the water, sent the mother-of-all understated text messages on Tuesday morning: "Hey dad, I am alive, safe now, love you, chat later."

But for every tale of survival, there's another of tragedy and a warning to those seeking its fabled barrels.

Bad weather and a big wave

When the group of Australians set off for Pinang on Sunday afternoon, the skies were sunny and the seas were calm. Foote and Weisse jumped onto one boat with Jordan Short and Will Teagle, while the rest of their friends piled onto the other.

When the group set off on their fateful trip, the skies and seas seemed calm. But bad weather can strike at a moment's notice in equatorial Indonesia, creating dangerous conditions for those attempting to cross its waters. Accidents at sea are common, largely due to overcrowding on ferries and boats, and sometimes the small vessels are simply no match for the heavy rain and treacherous swells.

Sure enough, about an hour into their journey, bad weather set in. The first boat took shelter near Sarang Alu to wait for the storm to pass. The other boat carrying Foote, his three friends and three Indonesian crew, continued on its journey.

A short time later, they were in trouble. The boat was being slammed by big waves from the back and side. Without GPS, radio, flares or emergency communication equipment, they had no way to send a distress signal.

Foote later recalled the moment they realised they'd have to get into the water to survive.

"When the first [wave] came in, Jordie's like, 'Alright guys, this could be serious…what do we need?'" he said.

The group quickly grabbed knives, head torches, fresh water, and their surfboard bags.

"As soon as [the boat] filled with the next wave, I was like, 'Alright, everybody get the f*** out now!'" Foote recalled.

"I jumped out, grabbed Steph…Will dove out, Jordie ran to the front of the boat and the boat started [tilting into the water]."

The group threw the surfboards in the water and jumped onto them to survive.

"The waves were high and we all discussed quickly and decided to swim to the nearest island using the last rays of sunset as our guide," captain Yunardi Ardi told the ABC.

The Australian surfers started paddling, while the Indonesians stayed floating near the boat. As night fell, they battled waves and were guided by the lighthouse of Sarang Alu.

It would mark the beginning of a long, cold wait at sea.

Lost at sea

By Monday morning, the worst of the storm had passed but the wooden boat was nowhere to be seen. While the group clung to their surfboards in the vast ocean, trying to paddle to dry land, an extraordinary search effort began.

Local Indonesian authorities sent two ships, a speedboat, and an aircraft to scour the area between Sarang Alu and the Banyak Islands.

The surfers were found between Sarang Alu and the Banyaks

Indonesia's search and rescue agency mobilised a massive air and sea operation, coordinating with local volunteers, Australian authorities and friends and family of those missing.(Supplied)

Meanwhile, local fishermen, charter sailboats, and vessels from private surf camps nearby all joined the search. Foote's father even chartered a local plane with the help of the Department of Foreign Affairs to sweep the area from the air.

The mission was coordinated by Indonesia's search and rescue agency, Basarnas, from the island of Nias.

Nirwan Ndraha, from the Basarnas rescue crew, said the first day was challenging, but they knew they had to keep going.

"It was a really difficult time because the weather was still really bad and the visibility on the ocean was minimal, so it was hard to find the victims," he said. "But at the same time we had to keep looking, so we were using all the resources we could to try to find them."

Despite their best efforts, by nightfall, there was no sign of the group.

An anxious search quickly turns to relief

By Tuesday morning, Basarnas finally got the news that few had dared hope for. Sea Mi Amor, a catamaran that had joined the search overnight, spotted three of the Australians clinging to their surfboards between Sarang Alu and the Banyaks. 

Another survivor, captain Yunardi Ardi, was picked up near Tuangku Island about the same time. And five minutes later, crew member Muhammad Iqbal was found. All the survivors were relieved when marine officers finally pulled them onto the boat.

"They were happy when they were found and their condition was healthy. They were really thankful to be found," Mr Ndraha said.

But Elliot Foote remained missing.

For several anxious hours, search teams continued looking for the 29-year-old who had paddled away from the group to find help, even sending up a drone to spot him from the air.

Finally, a local fisherman found Foote and took him to a nearby surf camp. Shortly after, the joint search team evacuated all six survivors to Pinang Island.

After their terrifying ordeal, Elliot Foote and his friends were reuinted to rest and recover (Instagram: Elliot Foote)

Basarnas chief Octavian, who like many Indonesians goes by one name, described the rescue operation as a huge joint effort.

"We found those survivors after we got information from the locals and private boat owners near Pinang Island. That really sped up the evacuation process," he said. "The skills and physical strength of the survivors [also] helped them survive 38 hours on the water."

Octavian, chief of Indonesia's national search and rescue agency known as Basarnas, coordinated the operation from Nias (ABC News: Mitch Woolnough)

How did they survive so long at sea?

After they were found, the Australians revealed they had made a series of decisions that likely helped to save their lives, grabbing equipment and water to help them in the ocean.

"There were some moments out there where we were quite nervous and didn't quite know what the outcome was going to be, but we just banded together," Mr Foote said earlier this week. "Every single moment, we just knew what to do and took charge and followed each other and there were no arguments. We were just strong as a unit."

While they escaped from the disaster relatively unscathed, survival experts say it could have gone very differently.

"The ocean has the heat of the desert, the lack of water of the desert, but it also has the freezing cold of the desert," survival consultant Gordon Dedmon told the ABC earlier this week. "Dehydration is going to kick in very, very quickly. Your ability to think clearly is huge. So water is definitely, by far, your main concern immediately."

Even though they were in tropical waters, the surfboards were crucial to the Australians' survival, according to Mr Dedmon.

"The water will conduct heat away from the body 25 times faster," he explained. "So they're lucky that they could get out because even in warm water, you'll go down the hypothermia route relatively quickly after being in the water for a period of time."

While the Australians have reunited with their friends, the search continues for the final missing Indonesian, Fifan Satria.

Fifan Satria, one of the crew members aboard the vessel that Elliot Foote and his friends were on, is still missing (Instagram: Elliot Foote)

But hopes of finding him alive are fading by the day. Octavian says it is possible he may still be found, and Basarnas will continue its search until Sunday.

"As long as he is wearing a life jacket, he could still be alive. But if not, I don't know what might have happened to him," he said.

The Australian survivors have now launched a crowdfunding campaign to support the 23-year-old's family as well to compensate those who helped rescue them. They also want to dedicate some of the funds raised to enhancing maritime safety in the Banyak region.

The unpredictable beauty of Sumatra

Sumatra has been popular with hardcore travelling surfer for decades, but has become far more accessible in recent years. Some have touted it as the new Bali — still relatively untouched, unspoiled and yet to be trampled by rampant tourism like some parts of Indonesia.

Just last month, Hawaiian surfer Mikala Jones died in a freak accident off Sumatra's west coast when his surfboard fin cut his femoral artery. In 2012, Sydney man Darren Longbottom was left paralysed during a surfing accident in the same area. And in 2015, two Australian surfers died a week apart off west Sumatra. The first hit his head on rocks in choppy surf, while the second drowned during a night-time swim.

Octavia said while people who plan to take trips in unpredictable waters need to be aware of the risks, Basarnas cannot stop people from enjoying paradise.

"We cannot stop them from surfing in the area, but we can suggest that visitors and Australian tourists should let us know if they're going in a wooden boat, prior to travelling to the islands," he said. "The weather in July and August is very bad, the waves can reach up to four metres and winds up to 25 knots so the weather is very unpredictable around Nias."

Despite the undeniable and Instagrammable beauty of the azure coastline, this incident will serve as a reminder that these waters can also be perilous, even deadly. For the survivors, the nightmare trip has left them in a complicated state of gratitude and grief.

"The last few days have been something that I cannot comprehend. My emotions are incredibly mixed; elation, guilt, complete adrenaline, anxiety, pure joy and happiness," Foote wrote on Instagram yesterday.

"My deepest thoughts are with the family of Fifan. Our joyful young guide who hasn't been found.

"I wish there was more we could have done to help you, and that will stay with me as a burden to bear. I understand the loneliness you must've felt in those hours by yourself."

While Foote and his friends spend their final days in the Banyaks recovering from their ordeal, Fifan's family is still searching for their son.

// LAUREN DAY and ARI WURYANTAMA

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