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A veterinary surgeon by profession, Challen has made notable dives in Cocklebiddy Cave and Pearse Resurgence. In 2010 he made a record setting 194 metre dive whilst caving in New Zealand. In 2018 he was involved in a cave rescue operation in Thailand to evacuate 12 children and an adult from the flooded Tham Luang Cave system. 
- "Archived copy". Archived from the original on 25 August 2011. Retrieved 24 March 2011.
- "Australian Honours" (PDF). Government Notices Gazette. Canberra: Commonwealth of Australia. 24 July 2018. ISSN 0819-7105. Retrieved 25 July 2018.