OK, "great" might be an overstatement for most but not me- they are Quonnochochaug and East Beaches I like them because like Napatree they are dead ends, made that way by breachways. Qunochochaug is closed to non locals all summer and East Beach (state) has limited parking.
Read in the Block island Times once about a guy who walked the periphery of the island, I don't know about that- the beach below Clayhead is all rocks....
I love Block island, we have a plan to go out there sometime and walk it north to south in a day, just waiting for the right time.