Su Düşen Şelalesi is a cascade in the hills beyond Termal, best reached with your own car or by combining a dolmuş to Üvezpınar with a hike or taxi. It is the sight that pushes Yalova beyond a simple ferry-and-bath day.
The waterfall is most rewarding as part of a slow loop through the forested interior, not as a rushed add-on from town. In summer, ask locally about minibuses from Termal before assuming you need a taxi.