Wireless Sensor Network (WSN) consists of sensors which are distributed in an ad-hoc network. Due to the limited power of sensors methods must be devised for sustaining network lifetime. Some approaches must be devised to increase sustainability of WSN i.e. efficiently utilizing power of sensors. In this regard the mobile sink may play an important role. As data is passed to user through mobile sink, they must be up for the longest time amongst all the sensors. Hence face the problem of energy depletion. Ways such as mobile sinks must be devised to overcome this problem.