Cruise ships are now so big and luxurious, that you will often fine many more luxuries than you would have expected. Multiple cinemas and swimming pools are now common places and even casinos.
The Casinos are of course a fun place to spend say £30 but be carefully not to spend your all your life savings.
Of course with most modern cruise liners the internet is speedy so you can always log into your favourite casino or bookmakers to use your recently acquired free bet.

Cruise ships are now so big that they can house an entire shopping centre within.

Although on your cruise you may have 4 ports of call, it is very easy to stay on your cruise liner for the duration of your cruise as there are many places to explore.