The popular "Nona Ana" passenger ferry from Dubrovnik to Sipan, Mljet, Korcula and Lastovo makes it easy to organise your own day trip from Dubrovnik during the summer.There is a Dubrovnik to Korcula ferry connection only in July and August. Note that there is an east and west harbour in Korcula and the captain normally decides at the last minute, depending on wind conditions, where to dock. It is also possible that the ship will leave from a different dock that the arrival dock, so make sure to ask.
Beginning on June 1, there is a connection to Sobra and Polace on Mljet Island. You'll want to get off at Polace rather than Sobra in order to visit the Mljet Island National Park. If possible, try to travel Wednesday, Friday or Sunday as those are the least crowded days.
On national holidays in Croatia, the ferry runs on a Sunday schedule.
The ferry is operated by G & V Line which has ticketing information and online ticket sales. Or, you can buy tickets at the dock 30 minutes before departure. In Dubrovnik you may buy tickets one hour before departure.