The basin of the Danube River extends over ten countries. The river is so wide that passengers in Calypso's helicopter, flying over the brown water, could not see the banks.

For two years, from 1990 to 1992, the Cousteau team observed the river in the rhythm of the seasons: frozen with the ice in winter, flooded in spring, nearly dry at the end of summer, the Danube yielded its environmental riches. By canoe, inflatable, icebreaker and helicopter, on foot and in the water, the crew of Calypso captured material for four films (The Curtain Rises, Charlemagne's Dream, Cries of the River, Rivalries Overflow), scientific reports and many articles about this adventure through the countries of Eastern Europe.

The plain of the Danube is as wide as a sea. It was the wheat basket of Europe until the early 20th century and sometimes life seemed to have stopped still in that area. Some 120 tributaries drain 805,000 square kilometers of basin into the Danube's 2,850 kilometers, making this the preeminent river of Europe.
It was the hyphen between eastern and western Europe. It opened them up to the world, witnessed their chaotic relationships and still concealed their exceptionally well-preserved areas.

In September 1990, Captain Cousteau carried out a complete survey of the river from its source in the German Black Forest to its immense delta in the Romanian Black Sea. To do this, the Cousteau team had to cast a fresh eye on this river so charged with history. They acknowledged its European dimension, even as each country along its path tended to appropriate the river for its own use. The outcome was a voluminous synthesis of findings that was distributed to some 1,600 scientists, decision-makers and journalists.

Assisted by roughly forty European experts, Cousteau scientists were particularly concerned by problems linked to energy, pollution, navigation and the protection of natural areas. They were able to formulate precise recommendations for each country involved, and proposed the creation of a High Council of the Danube to be responsible for studying projects related to the river by integrating environmental, technical, economic and social factors - a multidisciplinary vision of ecological problems close to Captain Cousteau's heart.