The town of Janitzio, which means "where it rains", is located atop the hill. Janitzio can only be reached by boats which run regularly back and forth from about 7:30 am to 6 pm, accessible from Pátzcuaro's pier (embarcadero). These boats can be hired to take you around other parts of the lake. The town is famous for the butterfly fishermen who are skilled at lowering their butterfly-shaped nets to catch the local famous cuisine "pescado blanco". The butterfly fisherman were also located on the back side of the 50 peso Mexican banknote.
http://en.wikipedia.org/wiki/Janitzio