If you travel 5-10km south of SV, you can visit Rapid Bay which has a really long jetty, currently closed for renovation. but if you walk north along the beach near the jetty, it will lead to a huge cave that is really impressive. bring a torch if you plan to do a bit of spelunking. ;)
A little bit east of Cape Jervis is Deep Creek Conservation Park, which is spectacular for hiking, fishing and observing wildlife. see my "Rapid Bay" VT page for a couple photos from Deep Creek from eons ago when we went there last. its a good place to see lots of roos in the wild fairly up close. i think Deep Creek is about 20km from SV.
Cape Jervis Rd, Second Valley, SA, 5204, AU
There is an incredible wind farm that is worth checking out ... you can catch glimpses of the windmills on your drive down to Rapid Bay. if you go a bit farther south of Rapid Bay (back on the main road), look for a sign on the left side of the road for a church tellign you to turn right. turn right here, drive up the hill, past the church and follow the road for a couple KMs until you are nearly underneath one of the 23 windmills ... there is a big sign with info about the wind farm right alongside the road. some signs along the road say local traffic only but we considered ourselves local and went anyways. definitely worth a visit. :)