Oneonta Gorge is a cool mossy canyon with high walls and year-round cold water. Lower Oneonta Falls is located at the end of the gorge (approximately 0.25 mile from the History Highway). Expect to get wet no matter what season... even during Autumn, when the water may be ankle-high throughout, there is one section just before reaching the waterfall where the water will be waist-high (and ICE COLD).
Note that there is a significant log jam near the mouth of the gorge, which probably will not be moving anytime soon. It CAN be navigated, but you must be very careful in doing so.