Check this out:
Neonode (the tech company that developed the IR touchscreen tech used in quite a few ereaders) posted the above demo video a couple weeks ago. It shows a sealed ereader submerged in an inch of water.
Based on the menus, I think this is a stripped down Nook touch that has been sealed inside a custom case. As you probably know, Neonode makes the touchscreen component used in this ereader, and that makes me think this demo is more to show off the fact that their screen tech works in extreme conditions rather than an attempt to develop a a commercial product.
According to the Youtube description, the battery life is 4 days:
Powered by Neonode’s infrared technology – this e-reader doesn’t mind being submerged under water. The demonstration is done with a paintbrush to show the technology’s performance and fast response time. The device has been in the water tank for four days, and we didn’t re-charge it once.