High-performance routing protocols demand networks to achieve high throughput while minimizing energy consumption, which is crucial for enhancing energy utilization efficiency. Addressing this challenge, this paper proposes an energy-optimization routing protocol based on transmission timeout(EOTT) in underwater acoustic networks. During the route discovery phase, a backoff mechanism is utilized to respond to as many route requests as possible before replying, thereby controlling routing overhead. Additionally, an energy-balancing strategy is integrated aiming to balance network energy consumption. In the data transmission phase, a retransmission timeout mechanism is introduced for data monitoring and link validity assessment. Moreover, collision avoidance mechanisms are incorporated to mitigate collisions and enhance packet delivery ratio and throughput. Simulation and in-field experiments are conducted to compare this protocol with the Ad Hoc on-demand distance vector routing(AODV) and vector based forwarding(VBF) protocols. Simulation results demonstrate that this protocol achieves improvements in both throughput and packet delivery ratio compared to AODV and VBF, with lower per-byte energy consumption. The underwater experiments further demonstrate that the EOTT improves throughput by 11.84%, packet delivery rate by 15.62%, and decreases energy consumption per byte by 0.10J.