The island isn't very big. The bus stops at a couple of places when it comes through, but the best way to get around is to walk, bike, or drive. Walking and biking are especially nice since there are several pedestrian/cycle paths.
Bicycle rental is possible from:
Freizeitcenter located at campground Sandseele, Bradlengasse 24 (north-west end). They have regular bikes, tandems and trailers for towing kids.
Schopflen castle ruins, (at the end of the causeway, just before you're properly on the island). Originally served as a point of defense for the island at low tide. Destroyed in 1366. Now it's got a platform that allows you to watch part of the wildlife sanctuary.free.
St. Maria u. Markus Cathedral. This was the abbey church and reached its present shape in the 11th century. The treasury (open Apr-Oct, 11:00-12:00 and 15:00-16:00, closed on Sundays) contains relics of St. Mark, among other treasures. Behind the cathedral is an herb garden, a reconstruction of the abbey herb garden.
St. Peter and Paul Church. Features late Romanesque wall paintings from the early 1100's and has rococo ceilings from the 1750's.
Georgskirche (St. George's church), (the first church you see upon arriving on the island). Contains relics of St. George, and wall paintings from circa 1000
Water sports. Rent a motor boat, paddle boat, canoe, kayak, sail boat or row boat. Take windsurfing lessons. All this is offered by the Freizeitcenter located at campground Sandseele, Bradlengasse 24 (north-west end).
Guided tour. Island tours are offered daily by the Freizeitcenter located at campground Sandseele.
Ice skate. If you happen to be here during the winter, and the winter happens to be a cold one, the lake will freeze in the bay beside the island. You can skate, play hockey, and buy mulled wine and currywurst from stands on the ice.