Charleston's flat terrain is ideal for bicycling, especially when it's warm. There are plenty of racks around town, and activists have been successful in getting some bike lanes and trails added in recent years. You can also bike to beaches over bridges and along old railways. Just stay alert and wear a helmet; many of the roads still aren't particularly accommodating to cyclists and drivers aren't always aware of you.
Charleston Water Taxi offers ferry service around Charleston Harbor, with stops at the aquarium, Patriot's Point in Mt Pleasant, the Charleston Harbor Marina (also in Mt Pleasant) and Waterfront Park. You can buy tickets online or on the boat.
There's also an app sort of like Uber, but for boats, called HOBA (www.hobarides.com). We're told it's a great way to get out on the water.
Car & Motorcycle
Most major car-rental companies, such as Avis, have offices at the Charleston International Airport. Be warned: parking is an issue. City parking lots charge around $2 per hour, and many hotels charge upward of $20 a night for parking.
Ridesharing apps are typically cheaper and easier than calling or finding a taxi, and many locals get around this way.
There is no train service for getting around Charleston.