This is Idriess's account of his experiences stranded on Howick Island with a companion (who went mad) on the Great Barrier Reef north of Cooktown in the 1920s. His original 1927 account (his first published book) was heavily fictionalised at the insistance of his publisher, but this 1938 re-write was categorised as "true adventure" so I've listed it here as non-fiction although it includes some dialog between the two men.