Harihareshwar is ideally located to explore this region of Konkan beaches. You can go beach hopping to Shrivardhan and Diveagar as well as the northern Ratnagiri beaches. Harihareshwar is located less than 200 kms from Pune and Mumbai, is not too close or too far away from either of the two cities. Just about an hour off from Mangaon on the NH17, road connectivity to Harihareshwar is also quite good.
If you are driving from Pune to Harihareshwar the best route is the Mulshi route passing via Tamhini ghats. Try to avoid the ghats after evening. The alternate route from Pune to Harihareshwar is via Bhor in which case one could get off the NH 17 from Goregaon. From Mumbai to Diveagar it is the NH17 that has to be taken uptil Mangaon. If you are traveling by a 2 wheeler you could take the 'sagari marg' and use ferry to cross the two creeks enroute.
Thanks to the ferries which also carry four wheelers across the creeks one could travel from Harihareshwar to right uptil Goa without getting on the NH 17. Suvarnadurga Marine services which connects Bhagmandala near Harihareshwar to Bankot opens up the option of visiting Dapoli and its beaches even during a short holiday to Harihareshwar. The ferries even take four wheelers across the creek