Manavgat River flows into the Mediterranean sea at southern coasts of Turkey. The river mouth being unstable shoals and shifts seasonally, preventing continuous navigation of boats and yachts through the entrance channel of river mouth. To stabilize the river mouth some alternative structures are studied and jetty type structure is chosen as the protection structure. The shoreline change of the Manavgat River mouth with and without protection structure is studied by using one line model for shoreline evolution. Two different sets of wave data (as seasonal or yearly averages) are used as the inputs of the model. The effects of different wave data sets on the shoreline changes are compared and discussed.