There is are several beaches on the Konkan coast of Maharashtra that still remain to unexplored by mainstream visitors. We had been to Ganpatipule which almost a 6 hr drive from Navi Mumbai.
Ganpatipule is famous for its 400 years old Swayambhu Ganpati Temple on beach of Ganpatipule beach is though crowded but it's quite vast so there quiet patches as well. Places to stay: There is a MTDC resort on beach itself, however to get a booking it's difficult.You need to book well in advance. But nonetheless there other small hotel around. We had stayed in Club Mahindra property 2 km away from the beach.
Don't forget to buy kokam syrup/sherbet of local produce .