No Screwing!

A married couple have been stranded on a deserted island for many years. One
day another man washes up on shore. He and the wife become attracted to each
other right away, but realize they must be creative if they are to engage in any
hanky-panky. The husband, however, is very glad to see the second man there. Now
we will be able to have three people doing eight hour shifts in the watchtower,
rather than two people doing 12-hour shifts.
The newcomer is only too happy to help and in fact volunteers to do the first
shift. He climbs up the tower to stand watch. Soon the couple on the ground are
placing stones in a circle to make a fire to cook supper. The second man yells
down, Hey, no screwing!
They yell back, We're not screwing!
A few minutes later they start to put driftwood into the stone circle. Again
the second man yells down, Hey, no screwing!
Again they yell back, We're not screwing!
Later they are putting palm leaves on the roof of their shack to patch leaks.
Once again the second man yells down, Hey, I said no screwing!
They yell back, We're not screwing!
Eventually the shift is over and the second man climbs down from the tower to
be replaced by the husband. He's not even halfway up before the wife and her new
friend are hard at it. The husband looks out from the tower and says,
"Son-of-a-gun. From up here it DOES look like they're screwing."