Abstract Underwater wireless sensor networks are very different from terrestrial sensor networks in which sound is primarily used as a communication medium. This article reviews the key challenges posed by the underwater environment for developing effective underwater sensor networking solutions and introduces several new media access control (MAC) protocols with power control to increase efficiency and save energy.I. IntroduceUnderwater wireless sensor networks (UWSNs) have recently attracted increasing interest. It potentially has many applications in ocean graphical data collection, water quality monitoring, surveillance and national security purposes. The UWSN consists of a number of sensors that interact to send data to the land or surface sink node and perform collaborative tasks. Different applications have different reliability requirements. Data reliability is therefore one of the most important requirements for data transmission. However, ensuring reliable data transmission between the sensor nodes and the receiver node would be a difficult task, as the network performance is subject to the limitations and constraints of the complex underwater environment. In this paper review, the main challenges of UWSN MAC protocol design are introduced. Then, related works on existing reliable MAC protocols for UWSN are reviewed and summarized.II. MAC Protocol Challenges for UWSN[1]Compared to radio waves used in terrestrial sensor networks, which would have very high attenuation underwater, acoustic waves have better propagation characteristics in water, this which makes it the preferred method for underwater communications. Therefore, the acoustic channel is used as a link for communication in the underwater sensor...... middle of paper...... ey of the existing Media Access Control (MAC) for the network of underwater wireless sensors (UWSN). " (2010): na.Park, Min Kyoun and Volkan Rodoplu. "UWAN-MAC: an energy-efficient MAC protocol for underwater wireless acoustic sensor networks." Oceanic Engineering, IEEE Journal of 32.3 (2007): 710-720. Xie, Peng, and Jun-Hong Cui. "R-MAC: an energy-efficient MAC protocol for WASA 2007. International Conference on. IEEE, 2007. protocol for underwater acoustic sensor networks. “Modeling and Optimization in Mobile Device,Access Control for Underwater Acoustic Sensor Networks.” Wireless Communications, IEEE Transactions on 8.4 (2009): 1899-1909. sensor networks. “Network security, wireless communications and trust computing, for underwater acoustic sensor networks.” Underwater Technology (UT), IEEE Underwater Sensor Networks 2011. "Wireless Algorithms, Systems and Applications, 2007.