The new guy and the wife are VERY attracted to each other right away, but they realize that certain protocols will have to be observed. The husband, oblivious to the new chemistry floating around, is very glad to see the second man there.
"This is wonderful! Now we'll be able to have three people doing 8-hour shifts in the watchtower instead of two people doing 12-hour shifts."
The new man is only too happy to help, and in fact volunteers to do the first shift. He climbs up the tall tower and stands watch, scanning the ocean horizon for any ships. Soon the husband and wife start placing stones in a circle in order to make a fire to cook supper. The new man yells down: "Hey, no bonking!"
They look at each other and yell back: "We're not bonking!"
A few minutes later, they start to put driftwood into the stone circle.
Again the new man yells down: "Heeey, no bonking!"
Again they yell back, "We're not bonking!"
Later they are putting palm leaves on the roof of the shack to patch leaks. Once again the new man yells down from high above: "Hey, I said no bonking!!"
They yell back, "And we said we're not bonking!!"
Finally the shift is over and the new man climbs down from the tower and the husband starts to climb up. By the time he gets half-way up, his wife and the new man are already bonking their brains out. Once at the top, the husband turns around and looks down and says to himself: "Son-of-a-gun. From up here it DOES look like they're bonking.