They were good Catholics. They sang the Salve Regina. I don't know about sailors singing a hymn every night - perhaps they do - but the hymn "Eternal Father Strong to Save" is a hymn identified with the British Navy. If I remember correctly, the words are: Eternal Father strong to to save,
Whose arms doth bind the restless wave,
Who bidst the mighty ocean deep
Its own appointed limits keep.
Oh, hear us when we cry to thee,
For those in peril on the sea. There are, of course, additional verses, but I can only recall the first one from memory.