A lot of shanties have no real narrative flow, certainly no more than a couple of verses per subject. This is because they were work songs, and needed to be of variable length depending on the job.

Pick the best verses, keep a few in the bag for if the songs going down really well and drop them in if necessary. Also, bear in mind that sailors would often "chime in" with the odd verse, even if the song was led by a shanteyman. Apply this logic and you break up the song simply by using different voices.

Hope that helps.

Oh yes, we murder these songs because we enjoy singing them so much.

Cheers, Jon