The research in Underwater Wireless Sensor Networks (UWSNs) has gained momentum over the last two decades owing to the vast applications it supports like environmental monitoring, underwater exploration, disaster prevention, military, navigation assistance, etc. The sensor nodes deployed underwater have limited battery capacity. The main challenge is to design energy-efficient protocols facing the constraints due to peculiar characteristics and harsh underwater environment. The traditional layered approach is inadequate and insufficient for this purpose, hence Cross-layer Design (CLD) is the need of the hour that allows information exchange among the different layers to find an optimal solution with better utilization of scarce resources to improve the network performance. As far as we are aware, there is no survey paper available in the literature dedicated to CLD in UWSN's. We present the unique characteristics of the acoustic channel and its corresponding issues and challenges. The different proposals in the literature are categorized and compared based on the performance metrics. The basic approach for each scheme is detailed with its advantages and shortcomings which will help future researchers to overcome them to design efficient schemes.