Might be Miss Lucy Loo a halyard shanty. Last chorus goes.

We're rolling down to Trinidad to see Miss Lucy Loo.

If this is it, it's in the DT & Hugill's Shanties from the Seven Seas.

I also seem to vaguely remember a different one that has the above mentioned "sing sonny dor" (sp?) but I can't get past all the cobwebs. Barry