From 16 Euro (1 zone), 22 Euro (2 zones) and 29 Euro (3 zones), 1 day travel in the Bodensee area (Feldkirch, Bregenz, St. Gallen, Schaffhausen, Konstance, Friedrichshafen, Ravensburg...) by train, bus and 25% off by boat (from Friedrichshafen and Meersburg only)
Lindau and all the Bodensee area is very easily reached by train and car, the Lindau railway station is just opposite the harbour. And in the warm season numerous boats serve all German, Swiss and Austrian towns and resorts around the lake. And in a touristic area where three expensive countries meet you can be sure that these trips are not cheap but if you spend some time you can find the one or other deal combined with other attractions around the lake like excursions to the Mainau island or by funicular up to the Pfaender mountain above Bregenz which may be cheaper than the sum of the tickets needed for it.
The 70km or so of E54 from Singen down the East side of Lake Konstanz to Lindau was a very scenic route but queued solid with day trippers in August and it took a very frustrating 2+hrs to negotiate.
Don't let thatput you off though as the beautiful historic old town which is actually an island in the Bodensee is well worth the trip. Although heaving with tourists the town is very picturesque with fantastic views across the lake to the Suisse alps.
The train stops here enroute from Munich to Zurich and vice versa. From Bregenz, it is about a ten-minute train ride and costs $3 one-way. The train stops on the island and once you exist the station, the lighthouse and lion view are on your right, about 100 yards.
In the summer there are 4 boats per day to Rorschach, Switzerland, 11 Euro