Last February, we stayed at Hilton Head Harbor RV resort (its only a 45 minute drive from downtown Savannah) and it was great. Most of the sites are privately owned but are available for rental whenever the owner is not there. The sites are full service and immaculate, with large concrete pads and lots of palm trees, co-located with a seafood restaurant, daily garbage pickup, free WiFi. The site we got (#52) the owners had really gone all out with the landscaping... multilevel done with pavers, table, chairs, firebowl, plantings, lighting, etc. At that time, waterfront sites were $69/night ($64 for 4 or more nights) and non-waterfront were $59/night ($54 for 4 or more nights). There's a nice nature preserve (on Pinkney Island) about 5 minutes to the east.
2015 Rockwood Signature UltraLite 8282WS Platinum, GY Marathon LRD, TST 507RV TPMS
2005 GMC 2500HD CCSB D/A, Curt E16, Prodigy P2, Garmin RV760LMT w/BC-20 b/u cam