I just came back from two weeks of sun, sand and sea with my Cybook in a Aquapac PDA Classic Plus+ (Code 360).
Without that bag I doubt I would have even taken it to the beach being too worried about sand and sun-lotion.
I read 11 books and my cybook was totaly safe - the bag is a perfect fit and makes sure you can read and realy relax in "dangerous" environments.