Chennai Cooperative Housing Society - Society sold land that has run into encumberance issues

We bought land from a so called reputed housing society in Chennai in ****. While registering Society guaranteed that the land purchased would be free of encumbrances. However, now, we find that the survey number in which our plot is part of is identified as waterbody and our land is now in-directly taken away from us. Causing loss of hard earned money invested and the interest money that would have accrued if it had been put in bank