Hi, Phil
I don't like interrupting your excellent research but I think someone should point out that your subject 'Maritime work song in general' appears to have very tentative links to what you are posting.

The idea behind all of these 'work songs' is that the singing or chanting is an aid to the actual work. 'I acknowledge your 'might be' but all I see here is that the mariners were actually singing for other reasons than assisting their work. Seemingly totally religious reasons in this case.

The use of singing/chanting whilst rowing is well documented in many cultures.

Keep up the good work anyway.