Driven by the huge demand to explore oceans,underwater wireless communications have been rapidly developed in the past few decades.Due to the complex physical characteristics of water,acoustic wave is the only media available for underwater wireless communication at any distance.As a result,underwater acoustic communication (UAC) is the major research field in underwater wireless communication.In this paper,characteristics of underwater acoustic channels are first introduced and compared with terrestrial communication to demonstrate the difficulties in UAC research.To give a general impression of the UAC,current important research areas are mentioned.Furthermore,different principal modulation-based schemes for short-and medium-range communications with high data rates are investigated and summarized.To evaluate the performance of UAC systems in general,three criteria are presented based on the research publications and our years of experience in high-rate short-to medium-range communications.These three criteria provide useful tools to generally guide the design and evaluate the performance of underwater acoustic communication systems.