Relationships between distance

transmit power and frequency of single link in underwater wireless sensor networks（UWSNs） are analyzed

a centralized scheduling method based on cross-layer is proposed

access point（AP） through broadcasting beacon collect and estimate information of delay and distance of each node

in MAC layer

AP schedules every link by considering delay features of underwater link to avoid collision;in physics layer

transmitting power and frequency of nodes are changed adaptively to decrease energy consumption.Simulation results show that the proposed scheme can decrease collision and improve throughput as well as save energy consumption.