An ocean liner sinks in a big storm and there are only four survivors, who all are lucky enough to be in a lifeboat that washes ashore on a small island.   The island has a fresh water stream, plenty of vegetation, and plenty of room and material for shelter.   The only survivors are three guys and a woman.

After a few weeks of livinng there, they all come to the agreeance that they are in fact, all human and have sexual needs, so they set it up that the woman will rotate having sex with each guy every 5 days.  

So, they live happily like this for years, until the woman dies in her sleep one night.   The guys try to decide what to do, so they decide that life goes on.  Nothing will change between them.

After two weeks in the hot sun, things became unbearable, so they had to bury her.