Based on the true story of an evacuee ship that was torpedoed during the second World War, Lifeboat is about hanging on for dear life, writes Mary Leland

'We thought we'd just go to Bishopstown swimming pool," says Belinda Wild as she explains her quest for an approximation of a shipwreck experience in preparation for rehearsals of Lifeboat, which she directs.

Opening tomorrow in Cork's Half Moon Theatre, the play is the story of how two young girls kept themselves afloat and alive after their ship was torpedoed in the second World War. Fourteen-year-old Beth Cummings and 15-year-old Bess Walder were among 90 child evacuees aboard the passenger liner City of Benares on their way to safety in Canada in 1940. When the protective convoy had escorted the ship out of what was thought to be the danger area, two things happened: one was an immense and terrifying storm, the other a torpedo launched by a prowling German U-boat. Most of the crew and adult passengers and 77 of the children died in what was the worst British loss at sea up to that point in the war.

Written by Nicola McCartney of Belfast, now Creative Writing Fellow at the University of Edinburgh, Lifeboat was commissioned by the Catherine Wheels Theatre Company and won the Barclays Theatre Award for Best Show for Children and Young People in 2002. "This is a story that almost tells itself," says Wild. "Those two girls, as they were then, are still good friends, even though they had only met one another four days before the sinking. And it's that friendship which is the undercurrent of the play. They probably survived because they were together. It's the adults who were also clinging on to the lifeboat who let go, one by one, but the girls kept on telling one another to hang on, hang on. That's the main theme, really, hanging on."

Because this is a true story Wild felt a special responsibility to try for authenticity, to be as true to the reality as possible. So there had to be some swimming around, somewhere. Although the two actors involved have to play a total of 16 characters the emphasis has to be on the central figures clinging, literally, to the wreckage.

A contact with the National Maritime College at Haulbowline near Cobh introduced the cast to the "sea-survival pool", 10 metres deep at its shallowest and maintained for their benefit at a "cold enough" Atlantic temperature of 20 degrees. Boiler suits were provided to approximate the weight of clothes the girls were likely to have been wearing with their life-jackets.

In 1940 they were hanging on to the keel of their upturned lifeboat (number 5) but to allow for movement on stage this has been changed to a rope around the keel, all of which was simulated by the college staff who provided the boat and turned it upside down and then produced waves along with thunder, lightening, rain and darkness.

As a rehearsal venue this may have seemed ideal, although Aideen Wylde, who plays Beth Cummings, felt she would not have been able to hold on. "But you can't know, can you?" says Wild. "Some of the lines are verbatim. We relived them in the pool, and it gave us a physical foundation to work on, a sense of something close to what it might have been like, even some of the sensations that they talked about feeling at the time, their legs slipping, their hands freezing."

This is McCartney's first play for young people. Having trained as a director in the North of Ireland with Charabanc and encouraged by a bursary from the North of Ireland Arts Council, McCartney has also worked with Glasgow's Citizens' Theatre and, with the assistance of the Arts Council of Scotland, formed her own theatre company - Lookout - with the aim of finding new writing. Now, however, she concentrates on her work as a playwright, and on The Lion of Kabul, her new play for Catherine Wheels. She believes she has learned a lot from the Lifeboat experience - not least from her contacts with the heroines.

Both women subsequently married - Bess to Beth's elder brother - but have dealt with their shared experience in different ways. Beth is extrovert and has used the ordeal as a contributor to war reminiscences, research and lectures, almost shaping her subsequent life, while Bess, whom McCartney has never met, is more retiring, understandably finding the memory distressing. "But it was a total gift to write about", says McCartney. "It's so life-affirming and so inspirational."

In the Half Moon Theatre, designer Olan Wrynne's abstract set is built to allow what Wild describes as something of "an actor's playground"; it has to provide spaces for a cosy home, an air-raid shelter, a ship's cabin, a deck and the sea.

Here Wrynne also has to provide the perfect storm; it was the storm, perhaps even more than the torpedo, which caused such catastrophic loss of life. Cut open by the assault, the City of Benares was already listing when the lifeboats were being lowered. Although all the passengers had been called to a lifesaving drill almost immediately after the ship set sail, the weather added to the confusion of the actual ambush. Lifeboat number 5 was let down too fast and at such an angle that many of the children already in it were flung out into the sea. Beth and Bess were among them but they somehow found their way back, found something to grip, found each other.

Wild has been working for the Cork Opera House since 2001 on a programme of Shakespeare productions for young people which often have a forcefulness and appeal to which adults are also attracted. She hopes the same will be true in this case: "I had lots of questions that I wasn't able to solve pre-rehearsal but the answer just evolved quite naturally once we got working on stage. I think it's a perfectly crafted piece, written with great sensitivity, with a sense of joie de vivre which is almost humbling, coming out of that incredible near-death experience. I think adults should be coming in flocks, to be quite honest!"

Lifeboat runs at the Half Moon Theatre in Cork tomorrow at 10.30am and 1.30pm; Wed and Fri 11am, Thurs 10.30am and 1.30pm and Sat at noon and 3 pm