You can get these quests from Port Master in Port Control when talking about jobs/tasks.
When talking to port master he asks you if you would help to return the logbook of to it's rightful owner. It appears that captain forgot it when he was visiting the port control. Anyway, you take the mission and leave the city. Ship should be close, usually it appeared to me right away when I entered the map mode. (one note, don't board the ship, launch a boat like in Lost Countryman quest and talk to the captain) Not sure whether you should return to port master after you talk to the captain, or captain rewards you, but this is basically all you have to do.
Port master asks you for help since ship was stolen that was under his "control". Anyway, you have to take off, sail the seas until you spot ship with red(purple) sails in map mode, after that, just follow the instructions in Captive Bride/Groom task, with one little difference - you must bring the ship back. Talk to port master, return the ship and collect the reward. You can strip the ship of cannons and sell them for extra profit.
Based on original from Skodarap's CoAS Site (used with permission). Original is here .