Wireless sensor networks can improve the efficiency for collecting information in underwater environments. In the past, researchers collected data under the sea by the way of both sending oceanographic equipments into water and recovering it at the end of mission. The whole process often took long time so real-time services cannot be supported. Wireless sensor networks can detect events and transmit the collected data to a data center immediately. However, current terrestrial routing protocols are not suitable in the underwater sensor networks. Due to unique characteristics in the water, the transmission performance and energy of the routing protocols are inefficient. This paper develops an energy-efficient routing protocol in underwater sensor networks. The protocol is designed to reduce the number of packets transferring in the network, and also decreases the needed energy consumption. The protocol has been evaluated using Network Simulator 2 (NS-2). The results show that the number of reduced packets is considerable.