Once in Naaleu (southernmost community in the USA) you can take a guided trip to the Green Sand Beach.
We stayed at the B&B (Mark Twain Inn) in Naaleu. Local LDS meetinghouse is .5 mile up the street.

To get to the rocky coast that marks the southern tip of the Big Island, about 52 miles southeast of Kailua-Kona, take the South Point Road turnoff from State Highway 11. The narrow drive to Ka Lae passes through twelve miles of open ranch land en route to the sea. A field of huge white wind turbines can be seen along the way, generating electricity for the region.

The road passes through an area designated as South Point Park before reaching the coastal waters. Visitors should be aware that the last five miles of South Point Road are quite rough, and using a four-wheel drive vehicle is recommended. The parking area can be found at the end of the road, about a mile past the fork to Green Sand Beach.

Read more: http://www.city-data.com/articles/South-Point-Ka-Lae-Naalehu-Big-Island.html#ixzz41W9r73ni