Abstract. The one of the main objectives of any energy efficient routing mechanism of Underwater Wireless Sensor Networks (UWSNs) is to extend the network lifespan. The characteristics of underwater environs and acoustic communications make to prolonging network lifetime is a challenging task. To achieve the same, topology control and optimize energy consumption is needed, which can be achieved through clustering. In this paper, we proposed a sector-based forwarding scheme through dividing 3D network in sectors of same size and dimensions. Forwarding takes place in a sector-by-sector in a single hop manner via some nominated nodes called sector-heads and gateway nodes. The sector-heads of each sector elected on the basis of residual energy of the nodes, and dynamically changed after reaching energy threshold decided to forward data packets. The gateway nodes are some boundary nodes utilize when sector-head does not have sufficient energy to forward data packets towards other sector- heads. However, the proposal utilizes the depth information to forward data packets. Hence, all the communication is done towards vertical direction in, each sectorhead adaptively based on the depth of a particular node. The proposal is evaluated and analyzed against some existing energy efficient routing mechanism, and the simulation outcomes reveal significant improvement in energy consumption, network lifetime, and packet reception rate of the network and reduces the overall network overhead.