My wife and I spent 2 weeks in the Caribbean in December 2007 to January 2008. We had originally hoped to be able to go island hopping by ferry through multiple islands in the Eastern Caribbean, but after a little research found this would be very difficult – and impossible for the islands we had chosen. Despite the relative proximity of many of the islands, the only transportation offered between them is often by a local airline. When there was a ferry, we found it was more expensive than the flight.
We settled on the combination of St Lucia, Martinique, Dominica, St Martin/St Maarten, and Anguilla.