Default [Q] backing case for xperia z2 tablet

I've just purchased an xperia z2 10.1 inch tablet to use on my boat as a navigation aid.
The tablet will get a bit of a beating when crashing over waves - so I want to protect it with a back cover.

(I've had a galaxy tab - which survived pretty well - but it was in an enclosed cover - and a pig to see through the cover).
The water resistant features of the z2 will be helpful here - hence why I only want a back cover.

Can anyone recommend anything?