good points Jim.
I would like to add that being rehearsed is important.
here is a person who was a working shantyman, stan hugill, singing a shanty presumably in the way he would have used it for work, as far as i am concerned this is perfectly acceptable for any singaround
https://www.youtube.com/watch?v=znW01dlU0n0
https://www.youtube.com/watch?v=zKgQ50IPOCQ