The movies offered on the ship will be pretty much the ones you watched on the flight to the ship.
Cruise lines and airlines get their onboard movies from the same sources.
First run movies are far too expensive for the mass market audience.
Just before the films are released on DVD to the public, promotional rental companies offer them to the airlines and cruise lines. First the films must be censored to avoid violating all the American Political Correctness rules.
Then the DVDs are shipped off to the ships and airplanes.
Since the ships have a bigger captive audience, for a longer time, they also supplement their offerings with very old films whose copyrights have expired.
Some cruise lines also offer a DVD library for loan or rent.