In an epic trans-Pacific voyage to highlight the benefits of recycling, a boat crafted from thousands of plastic bottles sailed into Sydney Harbour on Monday.
The "Plastiki" catamaran, made from 12,500 bottles and the brainchild of an heir to Britain's Rothschild banking fortune, was greeted by hundreds of well-wishers as it ended its 15,000-kilometre (9,000-mile) journey.
"It's totally overwhelming," said project head David de Rothschild, the banking scion and environmentalist. "We're so excited to be here."
The Plastiki, which takes its name from Norwegian explorer Thor Heyerdahl's 1947 Kon-Tiki expedition from South America to Polynesia on a raft of balsa husks, set off from San Francisco in March.
The boat, carrying six crew, travelled through a waste-strewn area of the north Pacific and made stops in the Line Islands, Western Samoa and the French territory of New Caledonia before leaving for Australia.
The Plastiki's bottles are lashed to pontoons and held together with recyclable plastic and glue made from cashew nut husks and sugarcane, while its sails are also made from recycled plastic.
The crew relied on renewable energy including solar panels, wind and propeller turbines and bicycle-powered electricity generators, and used water recycled from urine.
They were able to keep in touch with supporters via satellite through a website, blogs, and use of social-networking sites such as Twitter.
Skippers Jo Royle and Dave Thomson said sailing the Plastiki was "completely different" to any other vessel they had ever sailed, but that they had always been confident it would complete the journey.
"She's got here without ever a doubt in any of our minds," said Royle.
The idea was hatched after de Rothschild was left "dumbfounded" by a United Nations report into marine ecosystems and biodiversity, and the realisation "there are just these amazing human fingerprints all over our oceans".
And while he said the impact of the voyage had exceeded his expectations, the amount of degrading plastic floating in the ocean had confirmed the scale of the problem.
"Here you are in the middle of nowhere seeing ... these plastic items. They photo-degrade, get smaller and smaller, until they end up getting ingested by fish" which are then eaten by people, he said.
The United Nations Environment Programme says more than 15,000 pieces of debris litter every square kilometre (0.4 square miles) of the world's oceans, and another 6.4 million tonnes of plastic is dumped into seas each year.
De Rothschild declined to endorse either Prime Minister Julia Gillard or opposition leader Tony Abbott for Australia's August 21 elections, where environmental issues will be a key factor.
"I would urge any politician to give nature a voice," he said. "Vote nature first."
The Plastiki will be on display at Sydney's Maritime Museum for the next month.