PS - Judging from the Bahamian Letting Agent's ad here, the story that I posted about the Sloop John B being named after its Welsh captain, John Bethel, does appear to be commonly accepted as fact in the Bahamas - although confusingly, the ad is about a 19th century house which it says was built by John Bethel - which seems to scupper the idea that Bethel went to the Bahamas in 1647 or that the song could date from that long ago.

Can anyone throw any more light on this?

Dave