After walking and swimming up the Amazon River for six years and five months, Pete Casey has finally made it from the sea to the source of the Amazon!

The often agreed-upon source of the Amazon is Mount Mismi, Peru at 18,363 ft (5600m). Casey approached from the small mining town of Caylloma.

Camping at the base of Mismi (17,000ft, 5200m), Casey was joined by Piotr Chmielinski and photographer Zbigniew Bzdak who in 1979 made the first descent of the Amazon from source to sea. Trekking company owner Vlado Soto and guide Johan Sarate were also with them. The next day, on May 16, the five of them summited the mountain in a five-hour climb.

Casey seemed elated. "Thanks for all the brilliant messages. About time eh!! [...] Had an unforgettable day on Monday, Lots of photos and blog to follow soon. Now to walk [to] the Pacific Ocean," he tweeted.

To complete his journey, Casey plans to make his walk/swim across the South American continent from east to west.

He has already made his way down the western watershed of the Andes through what he referred to as "a dry, dusty, barren, lunar-type terrain strewn with rocks and boulders", to the village of Chivay.

He only has about 100 miles (160km) remaining in his expedition which he will cross by trekking the Colca Canyon, which he refers to as "the world’s deepest canyon".