This was told to me by a Liverpudlian ex-matelot:

It came to pass on the second Sunday of the soap and tobacco issue, Nabob the son of Pabob was making his way from Cosham to Portsmouth with the mess savings. He was rudely fell upon by thieves and vagabonds. He was ragged, bagged and shagged, hobnobbed and bobbed, and sent on his way rejoicing. Here endeth the first lesson.

The next morning he came aboard, adrift as usual. He was taken before the commander, who says unto him, “Jack, you have sinned, place thyself before the table”, which Jack did. He says, “Jack, cast thyself into the wilderness and die”. Jack cast himself into the wilderness and died, and thousands died with him, cos he was crab infested.