The RFA have had alcohol testing for many years, in line with civilian law. I have served on many RFAs as part of a squadron and as part of the Naval embarked support (now called MASF) and it works!
The Chof can test anyone he suspects is under the influence whilst on duty and kick them off to find their own way back from wherever the ship docks next.
The rules (if applied with common sense) are fair and don’t penalise watchkeepers or daymen either way and give ample opportunity to socialise (with alcohol) even at sea.
I agree that if a person “turns to” worse for wear, they load others, undermine discipline and put lives in danger.
All that’s needed is the Naval command to “grow a set” and start applying rules that already exist about drinking on board, but in the absence of that ever happening voluntarily, a test would force their hand to punish the offender. Good!
Cheers now