THE OPTIONS

Rescuers who reached a group of children trapped in a flooded Thai cave say finding them was the easy part; getting the youngsters out safely will be the real challenge. There is no simple solution for the 12 boys and their football coach, who are being looked after by Thai military divers and an international team of underground rescue experts. The path back to the entrance is long, cramped and at least partially submerged. And some of the boys cannot swim. And all have been weakened -- physically, and possibly mentally -- by 12 nights underground. Here are some of the options rescuers are mulling for reuniting the group with their waiting families.

WAIT FOR WATER TO DRAIN OUT

This is the safest and most straightforward option, but could take a long time -- possibly months. Japanese engineers have helped rig up a pumping system that is reducing water levels by one centimetre (half an inch) every hour. If they could keep that up, it might be possible to reduce the flooding enough for the boys to walk out. The problem is the weather. Heavy rains are expected to lash northern Thailand for weeks, soaking through the mountain and filling up the cave as fast as -- or even faster than -- water can be drained.

ESCAPE THROUGH A CHIMNEY

The cave complex stretches around 10 kilometres inside the mountain, and it is possible that there are undiscovered "chimneys" that could lead upwards and into fresh air. Rescuers know there is nothing leading to the part of the cavern where the boys are currently holed up, but there could be an exit deeper inside the cave. "We are mobilising all forces to survey the closest point to the place where children are, and are searching for a chimney there," said Chiang Rai province governor Narongsak Osotthakorn.

A COURSE IN CAVE DIVING

The most obvious option to lay observers -- teaching the boys to cave dive -- is the one most experts agree would be the trickiest and the riskiest. It takes a healthy adult around three days to learn to scuba dive, usually in calm, clear water, during daylight and with no obstructions overhead. The cave is dark, cramped and flooded with fast-flowing, muddy water, where visibility is sometimes only a few centimetres. The risk of something going wrong, or one of the boys panicking and endangering himself and the rescuers, is high. Torsten Lechler, a diving technical adviser from Germany who is assisting the rescue team at Mae Sai, said the complex is "snakelike", winding up and down with steep climbs and flooded areas where there would be no choice but to dive. These stretches are up to 15 metres long, with poor visibility or no light at all, and the group would need to rely on touch alone.

FLOATING 'PACKAGES'

An alternative to asking the group to make the long dive themselves may be to "literally bring them out in packages," British caver Whitehouse said. "If you imagine them in a stretcher with an air bottle, with a full face mask, and... float them out through this, where they don't have to swim themselves." Whitehouse said the method has been done on other cave rescues, although Thai officials have so far not mentioned this option. The cave's passages are narrow and winding and it is not clear if floating them out is possible.