I collected this song from Peter De Sausmarez of Sausmarez Manor St. Martins Guernsey. His ancestor, Philip Sausmarez took a leading role in the war of Jenkins Ear. Sausmarez was second in command of the Centurion, the most famous ship of its age in an adventure that rivalled Francis Drakes circumnavigation for daring. The reward for his four years at sea with George Ansonwas command of the Nottingham. The action with the Mars was his one and only successful engagement, only a few weeks after the incident decribed in the song he was killed in an undecisive skirmish off Brest. He is Buried in Southampton.
The song is clearly related to the "Dolphin" group of songs and an altered version of it appears on the Saydisc CD "Sea Songs and Shanties" collected by Peter Kennedy, (which incidently has a full colour picture of the Garthpool on the cover). On the Saydisc album this song is called the Warlike Seaman (or the Irish Captain), but the words make very little sense, in that ballad the ship changes home ports from Spithead to Liverpool and names from Nottinghan to London. However, the captain is called Somerville and this is a very close English approximation of the Guernsey French Sausmarez. There is a version of the Dolphin on one of Tony Capstick's albums on Rubber Records ( Does a Turn ) the last time I saw TC he was acting in Coronation Street ( the Folkies graveyard?).
Back to the song, I would speculate the Guernsey version is nearer to the original than that on Kennedys' recording, although of course the folk process will undoubtedly alter many songs over the years. The Guernsey version was printed as a Victorian parlour piece, the tune was over-arranged but in both lyrical and musical structure it was clearly a cetacean.
I have sent a copy of the words to Peter Kennedy for safe keeping in his archve in Gloucester