I was in Samana a couple of years ago and there is really nothing close to the ship that I remember being able to do. We went back to the ship after our excursion(jeep tour). Depending on how much time you have maybe you can book another excursion. Sorry I couldn't be of more help.
Carnival Legend:Western Caribbean
RCCL - Explorer of the seas: Bermuda - April 08
NCL - Spirit: Eastern Caribbean - April 07