A cruise on the Pacific goes all wrong, the ship sinks, and there are only 3 Survivors;
Bob, Tom and Debbie.
They manage to swim to a small island and they live there for a couple of years doing what's natural for men and women to do.
After several years of casual sex, all the time, Debbie felt absolutely horrible about what she was doing.
Finally, she felt so guilty having sex with both Bob and Tom that she killed herself.
It was tragic, but Bob and Tom managed to get through it. But, after a while, Bob and Tom's resistance to natures urgings waned, and the inevitable happened.
Well, a couple more years went by and Bob and Tom began to feel absolutely horrible about what they were doing.
So they buried Debbie.