SYDNEY — A boat made from 12,500 plastic bottles will leave New Caledonia for Sydney this week on the final leg of a voyage across the Pacific to raise environmental awareness, organizers said Tuesday.

The Plastiki, inspired by the 1947 Kon-Tiki raft expedition, has already sailed 6,944 nautical miles (12,860 kilometers) in 108 days from San Francisco to the French Pacific territory, via the Line Islands and Western Samoa.

The voyage, to highlight the dangers of plastic pollution, over-fishing and climate change to the world's oceans, is expected to start its last and most challenging leg on Wednesday — if weather permits — after arriving in New Caledonia last week.

British adventurer and ecologist David de Rothschild, the youngest heir to Britain's Rothschild family banking fortune, dreamed up the idea of a fully recyclable performing vessel after reading a UN report on ocean ecosystems.

He said it was inspired by Norwegian explorer Thor Heyerdahl's Kon-Tiki expedition from South America to Polynesia on a raft made from carved-out balsa husks.

The Plastiki's bottles are packed together in a "pomegranate-like" structure and fixed to pontoons, giving the catamaran 68 percent of its buoyancy, and it uses fully renewable energy sources including solar, wind and sea turbines.

It is held together with a fully recyclable plastic called Seretex and an organic glue made from cashew-nut husks and sugarcane, while its sails are also made from recycled plastic.