[4] He grew up in the Perth suburb of Thornlie and later on a 200 ha (500 acres) farming property in Gidgegannup; he attended Eastern Hills Senior High School in Mount Helena, near Gidgegannup.

[5][6] A veterinary surgeon by profession, Challen has made notable dives in Cocklebiddy Cave and Pearse Resurgence.

[8] In 2020 he made a second record-setting return visit to the Pearse Resurgence (New Zealand) and extended the Australasian depth record to 245 m (804 ft) with his dive partner Richard Harris.

[9] In 2018 Challen, along with his dive partner Richard Harris, was involved in a cave rescue operation in Thailand to evacuate 12 children and an adult from the flooded Tham Luang Cave system.

[11] On 7 September 2018 the King of Thailand appointed Challen as a Knight Grand Cross (First Class) of the Most Admirable Order of the Direkgunabhorn.