Second the digicel router. We bought the 110V version and it is rock solid. The pre-pay process requires a very specific sequence of behaviors. But, the ladies in the store can work it over the phone for you.

Check with your charter company to see if they rent access points. Otherwise, you'll need to hit a store in Road Town. Digicel also has a store in Spanishtown VG, but not walkable from marina.

Cheers, RickG