Cas and Jonesy are an Australian duo known for being explorers, endurance athletes, motivational speakers, as well as a writer and documentary producer respectively. Their given names are James John Castrission (born 14 March 1982) and Justin Roderick Jones (born 20 June 1983).

In 2008 they kayaked 3318 km across the Tasman Sea from Australia to New Zealand, becoming the first to do so.^[1][2]

On 26 January 2012, Castrission and Jones completed the first unsupported polar expedition from the edge of Antarctica to the South Pole and back without mechanical assistance. After 89 days they made it back to the coast, having skied 2275 km while towing sleds full of supplies.^[3][4] They arrived alongside Aleksander Gamme who had waited for them so they could all finish together.

Castrission was born in Sydney, the eldest of three children to parents John and Vivienne. Both sets of grandparents migrated to Australia from Greece after WWII.^{[citation needed]} He was educated at Knox Grammar School and then attended The University of Sydney where he undertook a Bachelor of Commerce (Finance & Accounting). He is married to his wife Mia and has a son. They reside in Blackheath, Blue Mountains.^{[citation needed]}

Jones was born 20 June 1983 the youngest of three children to parents Rod and Chintra Jones. He lived in Indonesia until he was 11, before attending boarding school at The Kings School Sydney. He later moved to Knox Grammar School. Jones completed his tertiary education at The University of New South Wales where he studied a Bachelor of Science (Honors Physiology). He currently resides in Tasmania with his wife Lauren and two daughters, Morgan and Dylan.^[5]

Castrission and Jones met when they were 15 and 16 respectively. Castrission 's family was Jones's home family in Sydney, assigned to him while he attended boarding school.^{[citation needed]} They became friends, sharing a common love of the outdoors. They participated in cadets together and upon leaving school, they began attempting a number of bushwalks and kayak expeditions together, while working separately in various roles. Castrission worked at Deloitte as an accountant, then management Consultant (2003–2007). Jones worked as a research assistance in a science laboratory (2004– 2007) and various pubs in Sydney.^{[citation needed]}

In 2007, Castrission and Jones decided to work full-time on their plans to kayak across the Tasman Sea. Since then, they have published books, filmed documentaries and given public speaking seminars based on their frequent expeditions.^[6]

Published in January 2010, the book Crossing the Ditch tells the story of Cas and Jonesy's adventure across the Tasman, paddling more than 2000 km kayak from Australia to New Zealand.

Extreme South was written by Castrission following the couple's South Pole excursion and was published in July 2012.^[20]

In the documentary Crossing The Ditch (aka 62 Days at Sea), Jones uses footage recorded during Cas and Jonesy's crossing of the Tasman Sea to tell the story of their kayak journey from Australia to New Zealand. The documentary features interviews from both adventurers.^[21]

In his second documentary, Crossing the Ice, Jones uses recorded footage and interviews to tell the story of the pair's journey over 1,140 km to the South Pole and back again, and the quest to become the first humans to achieve the feat unassisted.^[22]

Cas and Jonesy, under the Cultural Gifts Act, donated all the expedition equipment from their two major expeditions to museums in Sydney. In 2010, the Australian National Maritime Museum acquired and showcased equipment from their 'Crossing the Ditch' expedition, and as of 2018 it remains part of the collection.^[23][24]

The Powerhouse Museum accepted the equipment from their 'Crossing the Ice' expedition, and as of 2018 items are on display in the Expeditions section.^[25][26][27]