It is extremely important to stay hydrated but generally water is not required. Drinking water during a yoga practice can break your concentration. Why not drink a couple of glasses of water before the class to stay hydrated. Re-hydrate after the class.
During your first class, you can expect a welcoming environment, guidance from the instructor, and an opportunity to explore different poses and movements at your own pace.
You may bring your own water if desired! Although the studio does provide water if needed; otherwise, everything else, including mats and props are supplied.