The TNF Basecamp duffel is not waterproof. The bag itself is pretty much impermeable but the zippers are not water tight.
Other than that they are great bags. I travel quite a lot and my medium bag is indestructable. I use it as my suitcase as well as the bag to carry my climbing gear (both rock and ice). The bag has withstood sharp ice tools, crampons and ice screws with no ill effect.

If you want totally waterproof get something with a roll top like some other posters have mentioned. The Ortlieb stuff is real good.