The Otto Prohaska books by John Biggins

How could I not have heard of this 2005 book? Or its three sequels? Seems like a must for George MacDonald Fraser fans.

From Publishers Weekly

The Austro-Hungarian submarine service during WW I is the unusual setting for first-time author Biggins's exciting debut, a retro techno-adventure story that falls somewhere between Tom Clancy and Patrick O'Brian. In an extended flashback, centenarian Ottokar Prohaska, ending his life in a Welsh nursing home, recalls his participation in the earliest days of undersea war, commanding U-boats so primitive that every dive was an adventure. Biggins brilliantly reconstructs the turn-of-the-century Hapsburg Empire, where situations might be hopeless but never serious. Prohaska is a well-rounded, sympathetic character whose point of view perfectly reflects the navy's officer corps. He and his crew sink ships, kill men and endure depth charging. They carry a pretender to the Albanian throne and transport a camel from North Africa to Crete. Underlying the picaresque adventures of these pioneering submariners is the ever-present prospect of dying in a steel coffin, whether from enemy action, asphyxiation, engine failure or mud. Prohaska's war has no glory--only the satisfaction of duty in a cause they believed in. This is top-notch military fiction with a literary flair, must reading for fans of the genre.
     

From Library Journal

Looking back on his career as a naval officer in the Imperial and Royal Austro-Hungarian Navy during World War I, 101-year-old Ottokar Eugen Prohaska narrates his experiences as a submarine officer in the Adriatic and Mediterranean Seas from 1915 to 1918. Stark realism and finely crafted humor characterize this well-balanced account of the Austrian submarine service during the conflict. Humorous episodes such as flushing a toilet while submerged, known as "U-boat baptism," and transporting a camel by submarine from North Africa to Albania are interwoven with moments of terror such as depth charge attacks and gun actions with ships. Biggins's use of narration, his thorough knowledge of the Adriatic, and good technical detail make this first novel of a little-known area of conflict compelling reading for those interested in the sea fiction of the period. Recommended for libraries with sea fiction collections.
Harold N. Boyer, Camden Cty. Coll., Blackwood, N.J.