On the panhandle in Florida we stayed at Big Lagoon further east we were late making a reservation and were not able to get into Ft Clinch so we stayed at Stephen Foster Memorial right on the river. Nice park, large lots although not full service.
In SC there are four ocean front state parks. Hunting Island, Edisto, Huntington Beach, and Myrtle Beach. Now is the time to make reservations because the full service sections of Myrtle Beach and Huntington Beach all fill up quickly.
If you want to stay close to I-95 Santee and Givhans Ferry are good options. Here is a link to SC state parks: https://southcarolinaparks.com/