1. Nanjing Mingji Hospital: this hospital has advanced medical equipment and technology, and provides fitness equipment such as underwater treadmills.
2. Nanjing First Hospital: this hospital has several departments and specialized doctors and provides fitness equipment such as underwater treadmills.
3. Nanjing Jiangning District People's Hospital: This hospital has several departments and specialized doctors, providing fitness equipment such as underwater treadmills.
Please note that these are just some of the hospitals I found, and probably not all of them provide underwater treadmills. Please let me know if you need more information or help.