ha ha ha
PR would be the more well known short 2 1/2 hrs run, lol.
Samana isn't that close by watre than it appears on the maps, specially because on it's way back the boat has to run all the way along the coastline upwaves/against the current, so small boats are out of the discussion.
i have one boat doing the long runs, including island hopping(
PR is just the closest of 'em), but it is not a cheap transfer.
the boat i use for those rides is a 63ft Sea-Ray luxury cruiser.
if interested just drop me a mail or PM here on the bord.
the other option mentioned above, travelling the route via Sabana de la Mar and the Ferry by public transportation is one of the best routes you can take as an "private excursion", a real adventure throu real dominican life, if you are interested in real dominican lifestyle i would recommend that, but that depends on your style of travel and how many luggage you carry with you.
have fun
Mike