Is it necessary to pre-book ferries from Split to Hvar & Korcula in September?
From the Jadrolinija website: "RESERVATIONS ON LOCAL CAR-FERRIES, LOCAL BOATS AND HIGH SPEED CRAFT LINES IS NOT POSSIBLE EXCEPT ON THE FOLLOWING FERRY LINES: Zadar - Ist - Olib - SIlba - Premuda - Mali Lošinj Zadar - Rivanj - Sestrunj - Zverinac - Molat - Ist Zadar - Bršanj - Rava
Šibenik - Zlarin - Žirje
Taking a car, or just walking on? Walk-ons would be a lot less critical, but some ferries do sell out. I've heard recommendations to buy your ferry ticket in advance if you can (eg upon arrival in Split for the next day's ferry). Exactly how busy the ferries will be may also depend - I bet Sept. 1 is a lot busier than Sept. 30.