Dependant on the ships rules and regulations you may have the privilege to access guest on board facilities, such as the show lounges or bars. You should always remember that guests take precedence over staff in all areas, such as the use of lounge chairs by the pool or exercise equipment in the gym. Any restrictions that do apply to you as a crewmember will be explained to you by the management when you board your ship.
Most ships provide a crew gym, bar, internet café and some have crew pools and private sunbathing areas for you to relax with your friends, away from the eyes of the guests.