From friends that I have known that still have family in Jamaica... If they do go back and apear to be doing well for themselves the Jamaican gangs will extort money out of you via your family or simply not allow you to leave. I can confirm that the Jamaicans that do end up leaving would rather fly their family out than risk flying in. They do not like to mention this for fear of said family.
As far as renting a boat in Jamaica, they do have to pay the local gangs to start up your own business and it just is not worth it.
The same friends that I was refering to used to be fishermen and wanted to start a fishing charter to cash in on the tourism. Unfortunatly they had to venture here instead.