Three completely different days get sold on this island under the same two words. Knowing which one you are buying is most of the job.
Inshore is the estuary: Broad Creek, Skull Creek, Calibogue Sound, Port Royal Sound and the creeks that drain the spartina marsh. Boats are shallow skiffs and bay boats, runs are short, and the targets are red drum, speckled trout, flounder, black drum and the sheepshead that graze barnacles off the dock pilings. This is where families and first-timers should be. You are rarely more than a few minutes from land, the water is protected, and something is usually biting.
Nearshore means the artificial reefs and live bottom off the beach, starting a few miles out and extending toward the twenty-mile mark. Bigger boat, longer run, and a different cast of fish: Spanish and king mackerel, sharks, cobia in late spring, amberjack and triggerfish further out. It is the bridge between a creek trip and a serious offshore day.
Offshore on Hilton Head means the Gulf Stream, and that is a genuine commitment. The blue water sits roughly sixty to eighty miles off this stretch of coast, so a real Gulf Stream trip leaves at dawn and runs ten to twelve hours, much of it steaming. Mahi, wahoo, blackfin tuna and sailfish are the prize. If anyone in the party gets seasick, this is not the trip.
Two pieces of local practicality. Tide runs the inshore day completely, and your captain will pick a start time to suit the water rather than your breakfast. A six to nine foot swing moves fish on and off the flats and floods and drains the creeks twice a day, so an 11am departure is sometimes the good one and sometimes the bad one. And licences are handled for you: a charter operating under a valid South Carolina charter vessel licence covers everyone fishing aboard, so you do not need to buy your own saltwater licence. Confirm it when you book, because the coverage depends on the vessel being properly licensed and under hire.