Myself and my gf booked this as a means of exploring the bay by water and we were not disappointed. The tour itself is a full day tour from 10-6 at a leisurely pace with the tour guide telling us about the history of the bay and the many historic buildings that we came upon. Though my gf did not speak serbo-croation our tour guide was more than happy to converse with us in English. The captain and his wife were very accomodating, making us lunch and stopping wherever we liked for a swim. I would recommend this to anyone looking for a nice relaxing day on the water!
Tip: The city of Kotor get very busy very quick so if you are driving in I'd recommend trying to get to the city for 8-830am to avoid traffic, there is lots to do before the guide finds you and you won't have to worry about finding a parking spot.