In recent days, the underwater wireless sensor networks (UWSNs) require more energy-efficient routing protocol in order to conserve better battery life. In existing, the protocols such as depth-based, cluster-based routings have specific limitations. Simultaneously, the existing routings protocols mainly suffered with high energy consumption and scalability issues. In this research, the Improved Hermit Crab Optimization (IHCO) is proposed. The fitness function of IHCO prioritizes the energy efficiency, and dynamic, adaptive nature reduces the scalability issues. Initially, the routing process is done with network modeling for the less energy consumption. The sink mobility is employed to transmit the data in UWSNs by using sink nodes. With the effective sink node data transmission, the energy consumption becomes less with the direct transmission of data. After that, the proposed IHCO is employed for the energy-efficient routing in UWSNs by attaining results in terms of packet delivery ratio (PDR) (99.8), energy consumption (EC) (10.2), transmission loss (TL) (146), and end-2-end (E2E) (29) delay when compared to the existing cooperative energy-efficient routing (CEER) protocol.