Forty Fathoms Deep, a book about pearl divers in Australia, was first published in 1937.
I've found two versions of the artwork produced for the original edition by Edgar A. Holloway.
This version says "Second Edition" on the spine so I'm assuming it's how the artwork was originally presented.
I believe this version dates from a 1952 edition.
This 1979 edition features a cover by Walter Stackpool.
Edgar Alfred Holloway (1870-1941) was born in Doncaster. He was a war artist during the Boer War and became known for his illustrations of military uniforms. He later produced illustrations for The Boy's Own Paper and many children's books. He emigrated to Australia in 1930 where he continued to work as an artist. You can read more about him and see examples of his work at the excellent Bear Alley blog.
Walter Stackpool (1916-1998) was one of Australia's most prolific illustrators of genre fiction and is probably best known for his covers for the Larry King "I Hate Crime" books which were based on a popular radio series. He also worked on westerns and children books, including Little Golden Books based on TV series such as Skippy the Bush Kangaroo, Barrier Reef and Woobinda (AnimalDoctor).