Dubrovnik to Mljet - via prapratno

Dubrovnik airport to Prapratno
Can anyone tell me how easy it is to get to Prapratno from Dubrovnik airport? I am landing at 10.55am on Monday and I don't really want to hang around for the catamaran to mljet which doesn't leave until 19.10 and there appears to be a car ferry that leaves Prapratno at 13.00. Is this a mad idea? Do you have any suggestions?
Thanks

Yes I think it is better to wait for the catamaran. You can visit Dubrovnik during that day ! A bus is waiting for the catamaran to bring you anywhere else in the island.