On 20 June 1918 he was serving on HMS Nimrod H43 as an Acting Sub Lt RNR. HMS Nimrod was a destroyer launched in 1915 and sold in 1926. His Captain, of the Portsmouth based ship, was Commander Hugh Fletcher.
As a Proby Midshipman he served on HMS Calyx (ex SS Calypso). She was sunk by torpedo 10 July 1916West of Listafjord Norway. You will need to go to National Archives at Kew to examine the ships' logs to see where they travelled. I would contact Archives to see if they hold Calyx's ship's log. The Captain and 30 of her crew perished, so her Log might have gone down with her.