We didn't take an MSC excursion, but went on our own to Ocean World Park. When we just got off the ship, there were lots of taxis, the driver took us to Ocean World, waited with us until we bought the entrance tickets to be sure that we entered the park. When we were done, we just texted him, and he picked us up and then returned to the port. We had a relaxing day, swam with dolphins, enjoyed the shows. Probably, if we didn't have a 7 year old daughter with us, we would not spend the whole day there, but still, it was a great experience. The same driver suggested to take us to other touristic points, but unfortunately we didn't have time.
We'll stop again at Puerto Plata with another cruise and are going to contact the same driver.