There are several beaches to visit in the Charleston area. If you are wanting to do a day at the beach, Sullivan's Island has plenty of public beach access points. This is just a short drive from the downtown Charleston area. If you are wanting to extend your stay and do a beach vacation, see the link attached for all of the different options in the area!
When in Charleston, you have to explore Rainbow Row to see all of the colorful historic homes. While in the area, walk over to the Waterfront Park where you can get a view of the water and see more historic homes.
Adam and I eat at Bar 167 every time we are in Charleston. They have the best oysters, calamari, and margaritas!