hop in a pool suspended five stories above another pool on the deck of a ship that looks like the result of a mad scientist hybridizing the genes of an airport duty free terminal, a private athletic club, a five-over-one and the Evergreen Ever Given (with just a splash of Six Flags for flavor)
The training mission in the 2016 Hitman is a fake cruise ship. There's also a level on a riverboat in Blood Money.
One of the levels in Splinter Cell Double Agent is on an actual real cruise ship if you can stomach playing it.