Twelve Thai boys are expected to need medical help before they and their football coach can be rescued from the cave complex they've been trapped in for nine days.
The group were found miraculously alive by two British divers after they were cut off underground by flood waters.
The British team last week joined Army rescue workers as they searched the pitch black of the vast Tham Luang cave network in northern Thailand.
Footage of the moment they were found shows the team, dressed in their red strip, looking remarkably calm as they sit on a ledge.
"How many of you?" asks one of the divers. "Thirteen," comes the answer.
"Thirteen? Brilliant!" responds the diver.
The diver then tries to explain to the team that they will have to be patient before they can be brought out of their underground refuge.
"There are two of us. We had to dive," he says. "Many people are coming."
Initial reports suggested the boys were too weak to move immediately and would need medical attention before being extracted along perilous flooded passageways to their anxious families who have been holding vigil at the entrance.
The two British rescuers, believed to be Rick Stanton and John Volanthen, from the British Cave Rescue Council, were part of a team flown into Thailand early last week as hope began to run out for the missing footballers.
Outside the entrance a woman, presumably a female relative, clutched an iPad showing pictures of some of the boys, with relief and joy spreading over her own face.
The news was immediately greeted by jubilant cheering from exhausted rescuers who have worked around the clock in treacherous conditions to locate and retrieve the children.
Four British rescuers in total joined Navy Seals and soldiers in the desperate search.
The Britons reportedly descended a chimney, abseiling about 40m and sending back helmet-cam pictures.
One of the cavers, Rob Harper, said they were using old surveys as well as maps from recent expeditions to search the far end of the cave system, using a chamber-by-chamber check.
British caver Vern Unsworth, who is familiar with the 5km long Tham Luang cavern, also joined the search.
Other rescue teams used drones, dogs, underwater cables and drilled through the cave walls in their efforts to locate the group.
When word reached the families that the 12 boys, aged between 11 and 16, and their coach, 25, had been found, the Thai Government livestreamed the scenes to the nation, which has been gripped by the desperate search after they became trapped inside the 9.6km-long labyrinth by rising floodwaters caused by heavy monsoon rainfall.
Bill Whitehouse, vice-chairman of the British Cave Rescue Council, said he had expected the Britons to reach the group first because they were by far the most experienced involved in the search. But he said some of the hardest work was still to come as they co-ordinated a dangerous rescue.
"The were doing the push-ahead and laying down the guidelines for others to follow," he said. "It is completely restricted with very dark tunnels and poor conditions, mud banks and areas that need excavating.
"They pushed forward on each dive, laying line and clearing the way."
They were followed by Seal divers leaving dumps of air bottles for a rescue operation, he added.
Whitehouse said that when the Brits arrived last week they did a couple of reconnaissance dives to assess the situation. But conditions rapidly and "cataclysmically" worsened over the weekend as bad weather meant rising water and a strong current before the rain eased off and diving could begin again.
He added: "Diving them out will not be an easy process. It is difficult enough with just one person but when you have several terrified children who are not divers ...
"It will take a lot of planning, a lot of equipment and a lot of preparation."
In 2010, Volanthen and Stanton were commended for their roles in a dramatic eight-day search for a potholer who was attempting to map tunnels in the Ardeche Gorges underground tunnel complex in France.
They found his body 780m from the mouth of the cave.
The boys were found close to a large, airy chamber known as "Pattaya Beach" – located more than 6.4km inside the cave – where rescuers had focused their efforts in recent days.
The cave is one of Thailand's longest and a major tourist attraction during the dry season. Visitors are usually only allowed up to 800m inside because the cavern has a reputation for being difficult to navigate.
Officials said the boys knew the site well and had visited many times before, encouraging their frantic relatives that the children were athletic and strong and capable of surviving the ordeal by drinking rainwater.
The boys' families have been camping in the mud, praying outside the entrance to the cave, close to where the boys had left their football boots, backpacks and bicycles as they set off on their adventure.