Sent down: students conquer cave network 550m deep

They had to negotiate hundreds of metres of dark, cramped and treacherous limestone tunnels, with no idea what might confront them around the next corner and no hope of rescue should they make a mistake. But in the end, it was worth it.

Six members of a university caving team have become the first people to explore and map a huge cave network on the Greek island of Crete, descending more than 550m beneath the surface to discover a vast hidden cavern the size of St Paul's Cathedral's dome.

The team, who are all present or former members of Sheffield University Speleological Society (SUSS), travelled to the island in June. They had already visited the region several times, discovering a network of more than 350 uncharted caves in the Mavri Laki region of the White Mountains.

Exploring the caves had become something of an obsession for the leader of the expedition, 25-year-old Rob Eavis, who first heard about the network in 2005 while attending a caving conference in Athens.

In 2006, he returned with party of about 20 students, and in 2008 the group uncovered a promising deep shaft which they named "ColoSuss". Eavis – who has been caving since he was five years old – vowed to return this year to explore the system properly.

The team of six worked in two groups of three, taking it in turns to descend into the shaft and map the caves while their colleagues slept. By the end, the round trip to the deepest cave – a 60m-high cavern more than half a kilometre below the surface which they dubbed "Final Destination" – took about 16 hours.

"It's such a thrill to walk down a passage and not know what's round the corner," Eavis said. "But it's even more of a thrill when you realise that no-one has ever known what's round the corner, and that you're about to find out. It could be anything: a massive chamber, beautiful streamways – it's such a buzz."

As if navigating the tunnels was not difficult enough, the team's campsite at the mouth of the cave network was utterly remote, three hours' walk from the nearest track and seven hours from any village. A lack of rainfall meant that water had to be gathered by hanging a tarpaulin in a nearby cave and catching the drips, or by hauling it up the 150m entrance shaft.

Robbie Shone, 29, another member of the expedition, said exploring the cavern had been "the icing on the cake" after a wait of four years, but that the experience of doing it without any assistance had been just as valuable. He added that the mapping and surveying of the subterranean system was also "crucial" to the expedition's success: "There's no point going away on these expeditions and not returning home with a map and photographs to prove what you've found."

Coincidentally, the team discovered during their research that the only other team of cavers to visit that particular part of the White Mountains had also been from SUSS, who explored the area in 1982 with little success.

Dick Willis, one of the UK's most experienced speleologists who has explored uncharted cave networks in South East Asia, said the team's achievement was even more remarkable given the extremely inhospitable conditions in which they had to work.

"The fact that they are so young was definitely to their advantage," he said. "It requires a good deal of physical strength and stamina to be carting the gear around over the mountainside. Merely locating and entering a cave under these conditions is a significant achievement in its own right."