Make up Rules, Give Directions.
"Last one in the Jacuzzi, has to turn around and let us all snap her bra."
"Everyone on the your right, reach over and tug their pants down One Inch"
"There is a car with one headlight, The Pedito Rule is kiss the lady on your left."
"First one to leave the pool has to moon everybody."
I searched Married Ssex Games
This looked interesting:
http://www.angelfire.com/folk/sexual/sexgames/