Stay at Alto Cerro hotel in Constanza and take the excursion to visit Aguas Blancas. This is in the central mountains. You can rent a car to get there. Of course, you will need to spend the night.

If when you come the Elupina ferry is working, rent a car and visit Las Terrenas or Las Galeras in Samana, taking the trip to the El Limón waterfalls. You can hop across from Sabana de la Mar to Samana and then take the road to las Terrenas. I suggest you overnight. You can stay at Portillo, Tropic Banana or many other small hotels.