Purpose-built, ultra-modern and ready to fight environmental destruction on the high seas, Greenpeace's latest campaign ship, Rainbow Warrior III, made its maiden voyage Wednesday.

"It's a beautiful boat," captain Joel Stewart enthused as the ropes were untied to launch the 58-metre (190-foot) long sailing ship, distinct with its green hull, colourful rainbow and white dove on the side, into the River Weser towards the northern German port of Bremerhaven.

Twenty-six years after the original Rainbow Warrior was sunk by French agents in New Zealand while attempting to stop France's nuclear testing in the Pacific, Greenpeace supporters enthusiastically showed their support.

As the new multi-million-euro vessel passed by, some had gathered on the bank, letting off a firecracker and writing the words "We will be with you" in the sand.

The ship was constructed at the 161-year-old German shipyard Fassmer, with three million donors contributing to the initially estimated 23 million euros (32 million dollars) needed for the construction work.

In the end it cost less, Brigitte Behrens, Greenpeace's director in Germany said.

"For me, a Greenpeace militant for 25 years, this day is very, very important," she said.

"We are continuing what colleagues began many years ago by using a boat to denounce attacks on the environment," she added, recalling that one person had died in the 1985 operation by French operatives.

The new ship was due in Hamburg Thursday and in Amsterdam -- its home port and Greenpeace's headquarters -- on October 28.

After an initial tour in Europe, the 680-tonne ship's first mission will be to set sail for the American coast before heading along the Amazon in Brazil to campaign against climate change.

For its American captain, a Greenpeace stalwart of 22 years, the ship is perfect for this kind of campaign, being a sailboat and therefore leaving a very small carbon footprint.

The boat is powered by sails on its 50-metre masts, an electric motor allowing it to reach a top speed of 10 knots and a diesel engine giving it 15 knots. The hull was made in the Polish port of Gdansk.

Constructed to meet strict environmental demands, heat from the ship's engine, for example, is recycled to heat the cabins, while used water is treated and purified by a biological system.

Rainbow Warrior III is also equipped with a helipad, and a mast with a 50-metre-high crow's nest allowing boats involved in illegal fishing to be spotted up to 24 kilometres away.