Mid-Atlantic - Most accessible place to go to in the Hamptons of New York?

I don't have a car and I'm looking for an easily accessible place to go to in the Hamptons to go to. Is Montauk the place? Someone said that it cost $25/way and 4 hours on the train. Is that true? I'm just looking to go there for a day trip and them head back to Manhattan for the night.

See the information on the Long Island Railroad at mta.info

Montauk is about 3 hours. Montauk is all the way at the end of the island. Other places like East Hampton are a little closer on the same line. The fare is $25 one-way peak, $18.25 off peak. (You might be able to bring that down slightly by taking LIRR part of the way and then switching to local buses but the extra time involved will almost certainly make that not worthwhile.)

Are you looking for anything in particular - beaches, rich people's houses, parks, downtowns?

See the information on the Long Island Railroad at mta.info

Montauk is about 3 hours. Montauk is all the way at the end of the island. Other places like East Hampton are a little closer on the same line. The fare is $25 one-way peak, $18.25 off peak. (You might be able to bring that down slightly by taking LIRR part of the way and then switching to local buses but the extra time involved will almost certainly make that not worthwhile.)

Are you looking for anything in particular - beaches, rich people's houses, parks, downtowns?

Just mainly sightseeing (history and natural sceneries).