South Carolina has enough Atlantic coastline that asking for the state’s “best beach” is not particularly useful. The better question is what kind of beach trip you want.
Myrtle Beach and the Grand Strand
Choose this area if you want a large resort destination with entertainment, restaurants, family attractions and many accommodation options alongside the sand.
Hilton Head Island
Hilton Head offers a calmer resort atmosphere with cycling, golf and broad beaches. It suits visitors who prefer relaxation and planned communities to amusement-heavy nightlife.
Charleston-area beaches
Beaches near Charleston make it possible to combine historic sightseeing with ocean time. Different barrier-island communities have their own character.
Look for quieter coast
South Carolina also offers less developed coastal areas where nature matters more than entertainment.
Swimming conditions, storms, rip currents and beach rules vary. Always follow current local and lifeguard guidance.
I would choose one coastal base rather than trying to drive between beaches every day. Sand is more enjoyable when you are lying on it than when you are stuck in summer traffic looking for parking.