I have 2 recommendations.
http://gundulastropicaltreasure.com/
Nice German lady owns this place, we had a fun afternoon here! She also will provide transportation to/from resort you are staying at.
We had massages by the beach here. They also do the fish pedis. Souvenir shop. Mamajuana, and a full bar. Bought art from a local artist.
catamarantourspuntacana.com
Hispaniola Aquatic Adventures
Our party of 5 did the private catamaran 1/2 day tour. It included snorkeling, delicious seafood lunch in the water, rum drinks on the beach with an alcoholic horse (true!), tons of pictures of your group and more!
We had a blast! It was great being on the private tour, since we were able to have full attention by the crew. They let us play our music, decide how long to spend at each stop...It was the best excursion we've ever done on any vacation.
Seriously 5+stars and would do it again in a heartbeat!!