Inherited Pool Problem?

[ariasc]

Mi wife and I bought a house in New Jersey 2 years ago. The house has an in-ground vinyl pool for which we don't have much information available. The previous owner had lived in the house for only 3 years, and did not really know when the pool was built. The problem we are seeing now is that it looks like every year one side of the pool is caving in a couple of inches per year. The attached pictures show the state of it as found we we opened it this year. What I would like to ask, what are the options we have if we wanted to keep the pool. Thanks!