The basic requirement for development of a fishing harbour is that the adequate wave protection should be obtained at the berths and entrance. It is noticed that many fishing harbours especially in southern coastal states where wave attack is more severe, have been facing serious manoeuvring problems at the entrance. As a result, the accidents took place and the vessels have been found to capsize frequently with loss of lives. This hazardous event can be stopped by using suitable modelling techniques to provide required wave protection at entrance. In the present paper, the case study of re-engineering a fishing harbour in Thengapattinam situated in Kanniyakumari district of Tamil Nadu State of India has been discussed. Presently, the fishermen are facing the difficulties to operate their vessels near to harbour entrance due to the high and broadside wave actions and accidents have been reported. To avoid this situation, re-engineering solution had been suggested by using mathematical model studies for wave tranquillity. The studies were carried with various layouts of the fishing harbour in order to provide the tranquillity at the harbour entrance well below 1.0 m especially for the waves incident from the south direction. Considering the safe wave tranquillity limit inside the harbour as 0.30 m and 0.80 m at the entrance, a layout was evolved at CWPRS with 642 m total length of the western breakwater extended upto (−)12 m which would provide sufficient tranquillity inside the harbour as well as at entrance of harbour for entire year. As per the shoreline changes studies, it is indicated that the impact of proposed extension of the modified layout would be negligible on the shoreline.