Just to second Barry's point, Sam's Gone Away was our absolute best "kids" bit. Get them started and you can come up with the most creative shipboard billets (I wish I was the principal, aboard a man o war ...)

We also had good luck with the "Hey Ho Little Fishes" version we got from Eric Illot, late of Bristol.

Finally, Jonathan's "Waltzing with Whales" parody always worked well.