Hi I visited Dominican Republic last year. We stayed at the Gran Bahai Principe resort and did two excursions on this trip. The first was a really long day but we had the best time. It was a trip to Saona Island. They took us by bus to a marina and then by speedboats to a natural pool where we saw starfish and got to hold them. Then we jetted off to Saona Island where we had a BBQ, a bar and lots of loungers to hang out on the beach. We were then put on a catamaran and enjoyed a nice sail back to the Marina. The bus stopped at a Souvenir shop on the way back to the hotel. I wrote a review of this excursion on my travel blog http://dreamtravelmagazine.com/saona-island-dominican-republic-transat-holidays-motorboatcatamaran-excursion/.

The second excursion we took was a snorkelling excursion and swim with the sharks/stingrays. This was a half day excursion and included a catamaran ride to a reef for snorkelling, then into a netted area in the ocean where the sting rays and nurse sharks were. We were then treated to a catamaran ride along the coast of Bavaro Beach with drinks, music and it was lots of fun. Here is a link to that review. http://dreamtravelmagazine.com/marinarium-swim-with-the-sharks-stingrays-catamaran-excursion-punta-cana/

Shoot me an email if you have any questions I'd be happy to answer them.
Sharon