What are your plans after disembarkation? We took the shuttle to the Ravenna train station, $10. We took a train to Bologna around 9:30 AM. I prepaid by calling C&A but once onboard they will remind you constantly that you need to make departure plans, so you can also book onboard. Personally I wouldn't pay for the bus to Venice unless you're going straight to the airport. If you're staying in Venice take the train.