Hi Marc/Dani
The canyoning tour you describe definitely sounds a lot more physically demanding than the waterfall tour...It sounds like a lot of fun! My wife would have killed me if I had taken her on a climbing expedition like that one! It took a lot of sucking up for redemption after taking her on an excursion she really didn't want to do. The rest of us had a great time, though!
That tour was an exceptional value. The Air Transat rep did not offer it through the hotel because of the risk/insurance isuues, although I think some of the European carriers did offer it through their reps. We had met a taxi coordinator at the entrance to the Mambo and did a Sosua tour with him for less than 1/4 the price of the "official excursion". Along the way we were talking about the waterfalls and he offered to take us for $40USD, which we felt was a good deal. I later talked to someone else at the resort who had bartered him down to $25US pp, wow!
Dani, when we stayed in Punta Cana (Sunscape BG) two years ago I don't remember seeing anything like a waterfall excursion offered by anyone. The land seemed pretty flat in that area so I'm not sure how far you would have to go to find some mountains for a waterfall. We did not do any adventure tours at all while in PC as there was nothing out of the ordinary available and they were all horrendously expensive. Fortunately, the incredible beach in PC made us not waht to leave anyway.
I'll keep my eyes open, if I see a tour of interest I will post the details for you.
Regards,
Dave