So true,

I'm lucky to have a vocal range that lets me do a fair to decent job on most shanties. I'm not sure that I'd ever refer to my voice as pretty, though that is more in the ear of the listener.

I love doing ballads and sean-nos (still working on that). What's important is to sing what you enjoy and feel comfortable with. And it may well happen that you're at a sing-around and happen to be the only one who knows the words to a requested shanty...so take my advise and give it a try. :)