The only time your ship will be in for 6 months in a row is when it is in the shipyard for repair. This is no real vacation for you, as this usually entails working harder than you generally work over the course of the underway cycle.
Here is my ship's (carrier) schedule, more or less, for this cycle:
In shipyard from March-August of this year.
Underway for 2 weeks in September and all of October. Inport for November. Out for 3 weeks before Christmas. Out for 2 weeks in January and 2 weeks in February. In for most of March. Deploy from end of March til October.
This "out for 6, in for 18" months crap is rubbish. It's a line to make you think that you are going to be in port far more than you are at sea. In a year span, from October 2006-October 2007, my ship will spend 9 out of 12 months underway.
If you desire to be home more than gone, the Air Force is a pretty good option, plus, they have much better golf courses.