Given that Punta Cana is at the extreme eastern end of the island of Hispaniola all excursions involve something of a lengthy road journey. Most tourists if they take an excursion at all (a relatively small %) take a cruise on the Caribbean from Bayahibe to Saona Island. It's a forty mile bus ride from Punta Cana airport to the Caribbean which should take about an hour but is often made longer by using shuttles from hotels to a garage forecourt near the airport and the subsequent boarding a bus for Bayahibe. En route a stop is often made at a tourist tat shop. The cruise to Saona takes you along the shores of the Parque Nacional del Este and stops at a "piscina naturale" about a mile offshore. There were abundant large starfish here but dumb tourists killed many of them - hopefully the numbers recovered with many fewer tourists due to Covid.
If you do go to Saona the trip is usually by speedboat one way and catamaran the other. Imho speedboat out and cat. back is far preferable because of the onboard party on the return from Saona - you can't party on a speedboat.
I also am wanting to find an excursion that does not involve so much time traveling in a vehicle. Seems the Sanoa island is the number 1 excursion. Researching, it seems to be over an 8 hour day.