In order to stop cruise line from charging you for internet, you have to type "18.104.22.168. logout" in address bar, at the end of your session.
That is the only way to stop their system from keep on charging you. Clicking at the X and closing a window is the biggest mistake you could make.
In that case, the cruise line will be happy to inform you that your time has been "used", since you have most likely paid for a time-bound package.
Another way of putting this problem behind you is to purchase a package that let's you stay connected for all duration of your cruise, but that kind of service is available only at a very few cruise line companies, and revolves around $240/7 days.
A good number of average internet users are not experts, and use internet for basic things like email and news reading, so instead of typing "22.214.171.124. logout" in the address bar
, they type it in the Google search bar. That is most likely how you got here at this page.
So here it is, a photo guide to location where you exit your session, and stop cruise line from keep on charging you: