Due to the long propagation delay and high error rate of acoustic channels, it is very challenging to provide reliable data transfer for time-critical applications in an energy-efficient way. On the one hand, traditional retransmission-upon-failure usually introduces very large end-end delay, thus is not proper for time-critical services. On the other hand, common approaches without retransmission consume lots of energy. In this paper, we propose a new multi-path power-control transmission (MPT) scheme, which can guarantee certain end-to-end packet error rate while achieving a good balance between the overall energy efficiency and the end-to-end packet delay. MPT smartly combines power control with multi-path routing and packet combining at the destination. With carefully designed power control strategies, MPT consumes much less energy than the conventional onepath transmission scheme without retransmission. Besides, since no hop-by-hop retransmission is allowed, MPT introduces much s...