Continuing a series of investigations connected with the shore processes and bar shifting occuring at the entrance of the lagoon region of Cananéia, in the south coast of the State of S. Paulo, the author describes the methods that were used to observe the modifications of the shore line and shoals in the Ilha Comprida and Ilha do Cardoso. The mechanics of the beach erosion and consequent sedimentary processes are examined in detail and several conclusions are drawn in relation to the apparent periodicity and duration of such phenomena. The effect of the dynamic activity of ocean waters is considered and the importance of meteorological factors on such activity is emphasized. In order to continue the work already done a plan for further investigations is presented.