Well, the cover arrived.
So I thought I'd spread a little bit of information about it.
It feels like it's made of well, for want of a better comparison, condoms. What I mean is that it feels a bit rubbery to the touch, and it would seem to be quite elastic.
It's a little big for the Cybook - a little wide, quite significantly too tall. But that's not a huge issue.
The seal on the device is in the catch, however the seal only prevents water getting into the sealed pouch, it does not prevent water getting into the catch.
This means that when you're finished surfing (I'd imagine many people will want this to read "Surfing for dummies") then you cannot immediately take the Cybook from the cover.
You can very quickly and easily dry the outside of it, and I believe you should do this. However there is water still held in the catch, and the only way to expose this so you can dry it is to open the catch, and by opening the catch you open the seal which allows the water in the catch to drop down and get to the Cybook.
The only way around this would be to hold the cover upside down and then undo the catch, and from there attempt to dry it out while making sure the Cybook doesn't slide out. Not something I'm going to do, or would recommend.
As for how long I expect it would take the catch to dry out? Certainly hours....
Which means that when I use it in the bath I'll then have to keep it in the cover until I'm sure the catch has dried before restoring it to the original leather case. Which exposes the Cybook to damage, I guess.
Here's a couple of piccies of it to show you how it looks in the cover and the catch itself.
Cybook in the cover
Only below the red line is sealed