This is a goby (family Gobiidae). There are several genera with an elongate body, and the photograph does not show enough detail for a positive identification. If you allow me a guess I would suggest it might be a species of Vanderhorstia Smith 1949.
I have no experience of Indian fishes, but possibly a species of Glossogobius ??? Has representatives in fresh- and estuarine waters. Obviously check against a taxonomic key. Regards