I have been rowing the creeks behind Capers and Bulls Island for years. I have always wanted to explore the area further up towards the actual cape of Cape Romain but have only barely scratched the surface going fast in a friend's motorboat. It's difficult to find overnight parking, but you can either park at the Isle of Palms marina for a small fee or probably work something out at Buck Hall. I have heard that parking overnight at Garris Landing gets you a ticket.
Camping on Capers Island is a favorite. Call or email the state for a free permit. I forget who, but you can google it. There are two islands further north that allow camping Murphy and one other, but I forget the name. Of course, if you're sleeping on board any protected cove or creek bend would work.
I haven't personally, but you could probably sail all the way across Bulls Bay at high tide. It gets extremely shallow all the way across, as do all of the bays. The creeks can be quite deep.
Fishing is amazing in here. Oysters, trout, reds, shrimp, flounder. The occasional ray and small shark. I've heard stories of big shark sightings in Bulls Bay when the bait fish are running.
As with most of the water inside of the barrier islands, it's almost all salt marsh with labyrinths of creeks. Be prepared for twists and turns and getting lost. I like to take screenshots of aerial photos for reference so I'm not draining my phone's GPS. Don't know what charts offer in here. You'll find poles marking the channels here and there but the creeks mostly find their way through. If you're not in a hurry, it won't matter.