Basically she is stuck in a time loop in purgatory because of how she treated her son, she is doomed to repeat this over and over and over again always with the same outcome. It's a punishment. In the film they referred to Sisyphus who is a mythological Greek God who had to push a rock up a hill only to have to roll back down again before he got to the top, this lasted for eternity as a punishment-
http://en.wikipedia.org/wiki/Sisyphus
The boat was called Aeolus, Aeolus was the ruler of the winRAB in Greek Mythology, his name was shared by three characters who were very difficult to tell apart. In the film before the boat came the winRAB disappeared and then on the boat there were different versions of Jess who were very difficult to tell apart.
http://en.wikipedia.org/wiki/Aeolus
So in short she is being punished by being forever made to go through the same events and no matter how hard she tries the outcome is always the same. She is stuck in a time loop in purgatory because of how she treated her son.