In my researches I have come across rating deserters, but rarely is there a hint, never mind a doing, of a naval officer deserting his post and his ship. As a very brief snippet, I came across this Obituary of 1980 of a hardy army officer who had once been a midshipman in one of our Flag ships. The ship was based off the Cape in far away South Africa when WW1 started in 1914. He feared that the navy and especially his ship would not see any of the action which he was hell-bent on experiencing, so whilst ashore he reported to a local army barracks and duly signed on as a soldier. It appears that he didn't tell the navy that he wasn't coming back, nor did he mention to the army recruiter that he was already a member of the UK's senior service newly promoted to an acting sub lieutenant RN. I have heavily cropped the obituary (which for ease of reading has been retyped), but this guy was a goer and came back for more in WW2 winning the DSO.

  Colonel Sir Hugh Boustead, KBE, CMG, DSO, MC, FRCS, who died in Dubai on April 3 at the age of 84, was an adventurous character whose exceptionally full life included service in the Royal Navy, the British Army, general Denikin's White Russian forces after the First World War, and the Sudan Defence Force, and who also held several civilian appointments in the Sudan and Arabia.
  Born in Ceylon, the son of a tea planter John Edmund Hugh Boustead was educated at Cheam School and the Royal Naval College at Dartmouth, whence in 1912 he was posted as a midshipman to the flag ship of the Cape Station. After the outbreak of war however, he deserted his ship to join the South African Brigade in the hope of thus seeing active service on the Western Front; and his hopes were fulfilled.
As a consequene of his military zeal, Boustead received a King's Pardon for having deserted (as a sub-lieutenant), and was made a second lieutenant in the field after being wounded at Arras and awarded the MC.