Al, Do not despair, you will find some secret spots. AND...contrary to what the nay sayers are claiming about security and expulsion from the ship....apparently they have never done it.....it is not TRUE. They want you to have fun on your cruise. THe employees and security will not bug you and the one time I was caught, they quietly ducked away.
It all depends on what ship you are on but there are tons of nooks and crannies on the ship.....but you'll probably want to wait until 1-3 in the morning when everyone is in their rooms.
A few places I've "sexplored"....the golf course at 4 am, on top of the chairs they stack up about 10 high every night on deck, and hidden decks intended for staff passage that are on guest floors and completly isolated during the wee hours of the night when the staff is sleeping (you might do your safety drills in these "munster" areas).
Have fun and definitely stay away from the rails if you're drinking. Lol