It's not every theater performance that begins with the actors giving safety instructions and explaining the proper way to put on a life jacket. But that is exactly what happens when you go to see Purple Sails, put on by the Forman Brothers Theater on a boat named Tajemství.

The boat, which cruises the waters of the Vltava and the Labe, takes its name from a ship in Alexander Grin's story, on which the play is based. "It's a beautiful story, written in a very poetic language," says Matej Forman, the twin brother of Petr Forman, with whom he founded the Forman Brothers Theater. "It's dreamlike but at the same time it's about the very concrete problems of people living in poverty."

The story tells of a small girl called Assol, who lives in a fishing village and one day is told by a magician that when she grows up, a prince will come in a marvelous ship with purple sails and take her away. Despite being ridiculed, the girl continues hoping and longing for the sea. When a young captain falls in love with Assol after seeing her asleep on the beach one day, he finds out about her dream from the villagers and decides to equip his own ship with purple sails. He sails into Assol's village and makes the girl's dream come true. (The production is staged in Czech but is strongly visual, so language barriers shouldn't be a problem.)

According to Forman, Grin was so attached to the manuscript of this story that he carried it everywhere with him. "This [strong attachment] really shows through," says Forman.

Living in a landlocked country makes it especially easy for people to identify with the girl in the tale, says Forman. "Most of us can relate to this longing for the sea that we experience as little boys or girls."

In deciding to stage the play on a boat, the Forman brothers help fulfill this longing for the spectators. Now equipped with purple sails, a stage and seating for about 170 people, the tugboat was formerly used for transporting coal. The Formans transformed it into a floating theater five years ago when they created the performance as part of the Prague 2000 cultural project.

But the boat is more than just a theater setting. It becomes part of the play, and the audience, carried up and down the Vltava, becomes part of the story. "The environment, for us, always plays an important role," says Forman. "The movement of the boat, the experience of the voyage, helps create the atmosphere."

The fact that the audience buys boarding passes rather than regular theater tickets already helps transport people into a different world, he remarks. "People can't leave — they're on a boat — so it's inevitable that they become part of the performance."

Several years ago, the Formans transferred Purple Sails into a tent setting, where it became more difficult to create the illusion of a real sea voyage. Some solutions were simple. To create the atmosphere of a storm, for instance — which isn't so difficult on a boat being constantly rocked by the river — actors would walk along the outside of the tent and shake the walls. But ultimately there was no substitute for being on the water.

It has been over two years since the Formans last performed Purple Sails on the boat, and the crew/troupe is looking forward to being there again. "[The boat] is like a home to us," says Forman.