I`m just checking their site, somehow I found the answer to the question 'what does "protected tablet" means' that was asked earlier in the topic.
Quoting the site:
The tablet complies with all the requirements that apply to a marine navigation computer: it is dust and water resistant, has a highly contrast display that makes working in the bright sun a breeze (we also have a liquid ink modification), crash resistant, has a high capacity battery, has hardware buttons, and includes the highly developed BoatPilot chartplotter and BoatGod module support.
So it indeed is all about physical protection, as simple as that.