I only ever heard it from the generation before me in the family, Royal Marines and Portsmouth men, whose parentage included the Queen's Pilot, the hereditary heads of the Pilotage Service between Spithead and the Nore in the days of Queen Victoria.
The version they sang was the Trad version of The Mermaid, with the exception of the last lines of the chorus, "we poor sailormen go up-up-up aloft, With the land-lubbers lying down below-below-below, With the land-lubbers lyin down below". They also similarly doubled the last line of the verse.
They then almost certainly borrowed Arthur Lloyd's chorus, probably in WWI when it was a fairly common practice to wrap things up with some jingoism, "Rule Brittania, Brittania Rules the Waves, For Brittons never never never shall be " - and then reverted to the line from the song "Married to a Mer-ma-yid at the bottom of the deep blue sea."
Mind you, as the family originally hailed from Orkney, there may be some insider knowledge...



The family itself is from Orkney origins, so we begin to see a tradition