His WWI Navy record can be seen on fold3. HIs first posting, from 10 August 1915 to 27 Jan 1916 was on the Ganges. His first rating was BOY II.
https://www.fold3.com/image/61132260...a,denis,victor
https://military.wikia.org/wiki/Boy_...adult%20seamen.
The first two postings (Ganges and Victory I) were shore stations. If I am reading it correctly, the
third posting was on the HMS Theseus.
This should show his record (Couta.jpg) , which I put on my shared Google Drive:
https://drive.google.com/drive/folde...Mm?usp=sharing
(Note: The same record is also available (currently for free) from the British National Archives. I also put it as a pdf file on the Drive.)